Magnetoresistance effect element, magnetic head, magnetic reproducing apparatus, and magnetic memory

ABSTRACT

A magnetoresistance effect element comprises a magnetoresistance effect film and a pair of electrode. The magnetoresistance effect film having a first magnetic layer whose direction of magnetization is substantially pinned in one direction; a second magnetic layer whose direction of magnetization changes in response to an external magnetic field; a nonmagnetic intermediate layer located between the first and second magnetic layers; and a film provided in the first magnetic layer, in the second magnetic layer, at a interface between the first magnetic layer and the nonmagnetic intermediate layer, and/or at a interface between the second magnetic layer and the nonmagnetic intermediate layer, the film having a thickness not larger than 3 nanometers, and the film has as least one selected from the group consisting of nitride, oxinitride, phosphide, and fluoride. The pair of electrodes are electrically connected to the magnetoresistance effect film to supply a sense current perpendicularly to a film plane of said magnetoresistance effect film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 11/609,557, filed onDec. 12, 2006, which is a division of U.S. Ser. No. 10/400,690, filed onMar. 28, 2003, which is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2002-092998, filed onMar. 28, 2002, and the prior Japanese Patent Application No.2002-263251, filed on Sep. 9, 2002; the entire contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a magnetoresistance effect element, a magnetichead, a magnetic reproducing apparatus, and a magnetic memory and moreparticularly, to a magnetoresistance effect element which has astructure where a sense current is passed perpendicularly to a filmplane of the magnetoresistance effect film, and to a magnetic head usingthe same, a magnetic reproducing apparatus and a magnetic memory.

By discovery of the Giant MagnetoResistance effect (GMR) in thelaminated structure of magnetic layers, the performance of a magneticdevice, especially a magnetic head is improving rapidly.

Especially application to a magnetic head and MRAM (Magnetic RandomAccess Memory) of spin valve film structure (Spin-Valve:SV film) broughtbig technical progress to the magnetic device field.

A “spin valve film” has a structure which sandwiches a non-magneticlayer between two ferromagnetic layers. The magnetization of oneferromagnetic layer (called a “pinned layer” or a “magnetization pinnedlayer”, etc.) is fixed by an antiferromagnetic layer etc., and themagnetization direction of another ferromagnetic layer (called a “freelayer”, a “magnetization free layer”, etc.) is rotatable in a responseto an external magnetic field. And when the relative angle of themagnetization direction of a pinned layer and a free layer changes, agiant magnetoresistance change is obtained.

A CPP (Current-Perpendicular-to-Plane) type magnetoresistance effectelement which passes sense current to a perpendicular direction to afilm plane of such a spin valve film shows the still larger GMR effectcompared with a conventional CIP (Current-In-Plane) typemagnetoresistance effect element which passes sense current in parallelto a film plane.

On the other hand, a TMR element using the TMR effect (TunnelingMagnetoResistance effect) is also developed, which passes the current toa perpendicular direction as the CPP type GMR elements. However, in aTMR element, since the tunnel effect is used, when thickness of thenon-magnetic intermediate layer made of alumina, for example, is madethin, there is a problem that MR rate of change decreases rapidly.

In the case of a TMR element, in the state where alumina is not madethin, resistance is very high. When application to a magnetic head isconsidered, its adoption is difficult from a viewpoint of a shot noiseand a high frequency response. For example, in order to use for amagnetic head, AR (current passed area×element resistance) must be setto 1 Ωμm² or less. However, in the case of a TMR element, there is aproblem that MR rate of change disappears in this resistance level.

On the other hand, a CPP type magnetoresistance effect element has theadvantage which has larger MR rate of change compared with a CIP typemagnetoresistance effect element. In the case of a CPP type element,resistance of an element is dependent on element area. Therefore, whenthe miniaturization of the element is carried out, it also has anadvantage that the amount of resistance change increases. This advantageserves as a big merit in the present when the miniaturization of amagnetic device progresses. Therefore, a CPP type magnetoresistanceeffect element and the magnetic head using it are considered to be themajor candidates for realizing storage density from 200 gigabits persquare inch (200 Gbpsi) to one Tbits per square inch class.

In the case of a TMR element, since an insulator is used for anintermediate layer, element resistance becomes high too much. For thisreason, if the miniaturization of the element area is carried out,originating in high resistance and causing shot noise generatingpeculiar to a tunnel phenomenon and high frequency response degradationwill pose problems. For this reason, a means of realistic solution isnot found in application of a TMR element in high storage density of 200or more Gbpsi.

In MRAM, tolerance level of element resistance is comparatively widecompared with a magnetic head. It is thought that a TMR element isapplicable to MRAM of a first generation. However, also in MRAM, theminiaturization of the element area is carried out with improvement instorage density, and it is expected that a problem that the resistancebecomes too high comes out. That is, also in any of a magnetic head andMRAM, high resistance peculiar to a TMR element poses a problem withimprovement in storage density.

On the other hand, in the case of a CPP element using a metalnon-magnetic intermediate layer, since the element resistance is verysmall unlike the TMR elements, the amount of resistance change is smallwhile MR rate of change is large. As a result, it is difficult toacquire a high reproduction output signal. And in the case of spin valvefilm structure where realization possibility is the highest, only a freelayer and a pinned layer are provided as the magnetic layers. That is,compared with a case of the artificial lattice multilayer structure,thickness and interfaces which contribute to MR rate of change are bothinsufficient. For this reason, MR rate of change becomes remarkablysmall compared with a practical MR rate of change.

In order to solve a part of this problem, by laminating an oxide layerfor the CPP element which used the metal non-magnetic intermediatelayer, increase of element resistance is aimed at and the trial to raisethe amount of resistance change as for the same MR rate of change ismade (K. Nagasaka et al., The 8th Joint MMM-Intermag Conference, DD-10).

In the case of this method, a metallic low resistance area isestablished in pinholes in part of oxide layer, and it aims to obtain ahigh resistance by constricting the current. However, it is difficult toprovide pinholes uniformly. Resistance varies largely especially in astorage density of 100 Gbpsi or more for which element size of about 0.1micrometers is needed. For this reason, fabrication of stable CPPelements is difficult.

By this technique, an increase in large MR rate of change cannot berealized, but resistance is just adjusted. That is, though MR rate ofchange does not change, if AR is raised, it is expected that the amountAdR of resistance change expressed with the product of MR rate of changeexpressed with percentage and AR will improve. Since area whichcontributes to MR rate of change becomes small effectually, MR rate ofchange seen from the whole may increase.

However, since element size becomes small so that it becomes highstorage density, the resistance demanded from a viewpoint of a shotnoise and the high frequency response characteristic must be small. forexample, a case of storage density of 200 Gbpsi, tolerance level of AR(current passing area×resistance) is from about one mΩμm² to a fewhundreds mΩμm². On the other hand, in the case of 500 Gbpsi classstorage density, AR must be less than 500 mΩμm². This is because elementresistance becomes large, when the element size accompanying improvementin storage density contracts. Thus, it is required that AR should bemade small with improvement in storage density. Therefore, it is clearthat there is a limit in an approach to increase AdR (current passingarea×resistance change) by increasing AR while keeping MR at a fixedvalue. That is, the essential improvement in the MR rate of changeitself is needed with improvement in storage density.

In order to improve a situation, research of a half metal prospersaiming at the essential improvement in MR rate of change.

Generally, it is defined as a “half metal” being a magnetic materialwith which only either of the densities of states of a up-spin electronand a down-spin electron exists near Fermi level. When an ideal halfmetal is realized, two states of an infinite resistance state and a lowresistance state are formed corresponding to the two magnetizationstates of the pinned layer and the free layer of an anti-parallel stateand a parallel state. Therefore, MR rate of change of infinite size isideally realizable.

Such an ideal state may be unable to be realized in fact. However, if adifference of density of states of a up spin electron and a down spinelectron becomes larger than conventional material, an increase of MRrate of change does not remain in improvement in about 2 times, but arise of 3 times, 4 times, and still more nearly extraordinary fast MRrate of change is expected.

That is, unlike the conventional solution mentioned above, improvementin large MR rate of change becomes essentially possible. However, thereis a big problem which obstructs utilization which is explained below ina half metal investigated intensively now.

That is, the following material can be mentioned as a half metalmaterial investigated until now. CrAs of semiconducting materials, suchas NiMnSb of the CrO₂ and the Whistler alloy with rutile structures,such as Fe₃O₄ with spinel structure, LaSrMnO with perovskite structure,and LaCaMnO, ZnO, GaNMn. Many of these materials have a complicatedcrystal structure. For this reason, in order to form a high qualitycrystal, substrate heating to a high temperature or special filmformation technique is required. There is a problem that these processesare not easy to carry out in a creation process of an actualmagnetoresistance effect element. This is the first problem.

A problem mentioned above may be solved by improvement of film formationtechnology. However, there are the following problems as a still moreessential problem. That is, any case of half metal material known untilnow, a limit of curie temperature (Tc: in the case of Ferro magnetism)and Neel temperature (Tn: in the case of ferrimagnetism orantiferromagnetism) is at most 400K (about 100 degrees in centigrade).Since temperature which shows half metal nature (here, it is defined asThm) becomes the lower temperature side, there is a problem thatmaterial which shows half metal nature in room temperature is not yetfound. This is the second problem.

Thus, if half metal nature is realizable only at low temperature, theapplication to a consumer product is completely impossible.

In order to use it as an actual magnetoresistance effect element, halfmetal appearance temperature Thm must be at least 150-200 degrees incentigrade or higher. In order to make Thm high, it is required to makeTc or Tn higher. However, with material investigated until now, Tc or Tnbeyond room temperature hardly exists. Intensive research is made inorder to raise Tc and Tn, but a decisive solution which raises Tc or Tnin every material cannot be found.

There are the following problems as the third big problem. That is, evenif a half metal is realized in a single layer film, when it is providedin a multilayered structure like a spin valve, there is a problem thathalf metal nature in a laminated film interface is lost. This is becauseband structures differ in a bulk state in an interface of the laminationstructure. Although a half metal is realized in a single layer film,there is a problem that a half metal is unrealizable in an interface orthe surface. In a part of magnetic semiconductor material (CrAs), thereis a report that a half metal of high Tc was realized. However,generally in an interface of a semiconducting material and metalmaterial, diffusion is intense. For this reason, it is very difficultfor half metal nature to be made not to be lost in a junction interface.

When using these magnetic semiconductor material, it is desirable toalso constitute a non-magnetic spacer layer from a semiconductingmaterial, and the combination with metal material is not realistic. If aspecific material in an interface layer is not laminated in the case ofthe Heusler alloy material, such as NiMnSb, it is pointed out that halfmetal nature cannot be essentially realized (G. A. de Wijs et al., Phys.Rev. B 64, 020402-1). This originates in half metal nature being lost ina laminated structure interface, since symmetry in band structure of acrystal collapses near the interface.

With a CPP element using the Heusler alloy, even if measured at 4.2K orless cryogenic temperature which is the temperature below Tc, only MRrate of change lower than a spin valve film formed with the usual metalis observed. This is based on above explained problem.

With spin valve film structure, it must essentially be made a laminatedstructure. Since half metal nature will be lost near the interface, itis meaningless to pursue material which half metal nature by using asingle layer of a single crystal.

As other means, there is a method of using a half metal as a material ofa spacer layer. Here, a “spacer layer” is a non-magnetic layer whichdivides the pinned layer and the free layer in the case of a CPPelement. An improved result using a perovskite system oxide is reported.For example, although Tc and Thm are still low temperature, whenmeasured at temperature below Tc, a TMR element realized quite larger MRrate of change than a spin valve film of the usual magnetic material (J.Z. Sun et al., Appl. Phys. Lett. 69, and 3266 (1996)). However, it isdifficult to create the pinned layer, the spacer layer, and the freelayer using material with a special crystal structure like perovskite.And the above-mentioned second problem that Tc is low temperature isstill not solved at all.

Thus, in extension of research of a half metal studied intensively now,realization of a high MR rate of change is difficult even in lowtemperature. Even if it is realized, a still bigger breakthrough forrealizing large MR rate of change at room temperature will be needed.

SUMMARY OF THE INVENTION

According to an embodiment of the invention, there is provided amagnetoresistance effect element comprising: a magnetoresistance effectfilm having: a first magnetic layer whose direction of magnetization issubstantially pinned in one direction; a second magnetic layer whosedirection of magnetization changes in response to an external magneticfield; a nonmagnetic intermediate layer located between the first andsecond magnetic layers; and a film provided in the first magnetic layer,in the second magnetic layer, at an interface between the first magneticlayer and the nonmagnetic intermediate layer, or at an interface betweenthe second magnetic layer and the nonmagnetic intermediate layer, thefilm having a thickness not larger than 3 nanometers, and the filmhaving at least one selected from the group consisting of oxide,nitride, oxinitride, phosphide, and fluoride; and a pair of electrodeselectrically coupled to the magnetoresistance effect film and configuredto supply a sense current perpendicularly to a film plane of saidmagnetoresistance effect film.

According to other embodiment of the invention, there is provided amagnetoresistance effect element comprising: a magnetoresistance effectfilm having: a first magnetic layer whose direction of magnetization issubstantially pinned in one direction; a second magnetic layer whosedirection of magnetization changes in response to an external magneticfield; a nonmagnetic intermediate layer located between the first andsecond magnetic layers; and a film provided in the first magnetic layer,in the second magnetic layer, at an interface between the first magneticlayer and the nonmagnetic intermediate layer, and/or at an interfacebetween the second magnetic layer and the nonmagnetic intermediatelayer, and the film having at least one selected from the groupconsisting of oxide, nitride, oxinitride, phosphide, and fluoride; and apair of electrodes electrically coupled to the magnetoresistance effectfilm to supply a sense current perpendicularly to a film plane of saidmagnetoresistance effect film, wherein a product AR of an area A andresistance R is equal to or smaller than 500 mΩμm², where the area A isan area of a portion of the magnetoresistance effect film that the sensecurrent substantially passes through, and the resistance R is aresistance obtained between the pair of electrodes, or a resistance Rbetween the pair of electrodes is equal to or smaller than 100 Ω.

According to other embodiment of the invention, there is provided amagnetic head comprising a magnetoresistance effect element having; amagnetoresistance effect film having: a first magnetic layer whosedirection of magnetization is substantially pinned in one direction; asecond magnetic layer whose direction of magnetization changes inresponse to an external magnetic field; a nonmagnetic intermediate layerlocated between the first and second magnetic layers; and a filmprovided in the first magnetic layer, in the second magnetic layer, atan interface between the first magnetic layer and the nonmagneticintermediate layer, or at an interface between the second magnetic layerand the nonmagnetic intermediate layer, the film having a thickness notlarger than 3 nanometers, and the film having at least one selected fromthe group consisting of oxide, nitride, oxinitride, phosphide, andfluoride; and a pair of electrodes electrically coupled to themagnetoresistance effect film and configured to supply a sense currentperpendicularly to a film plane of said magnetoresistance effect film.

According to other embodiment of the invention, there is provided amagnetic head comprising a magnetoresistance effect element having; amagnetoresistance effect film having: a first magnetic layer whosedirection of magnetization is substantially pinned in one direction; asecond magnetic layer whose direction of magnetization changes inresponse to an external magnetic field; a nonmagnetic intermediate layerlocated between the first and second magnetic layers; and a filmprovided in the first magnetic layer, in the second magnetic layer, atan interface between the first magnetic layer and the nonmagneticintermediate layer, and/or at an interface between the second magneticlayer and the nonmagnetic intermediate layer, and the film having atleast one selected from the group consisting of oxide, nitride,oxinitride, phosphide, and fluoride; and a pair of electrodeselectrically coupled to the magnetoresistance effect film to supply asense current perpendicularly to a film plane of said magnetoresistanceeffect film, wherein a product AR of an area A and resistance R is equalto or smaller than 500 mΩμm², where the area A is an area of a portionof the magnetoresistance effect film that the sense currentsubstantially passes through, and the resistance R is a resistanceobtained between the pair of electrodes, or a resistance R between thepair of electrodes is equal to or smaller than 100Ω.

According to other embodiment of the invention, there is provided amagnetic reproducing apparatus which reads information magneticallyrecorded in a magnetic recording medium, the magnetic reproducingapparatus comprising a magnetic head having a magnetoresistance effectelement including: a magnetoresistance effect film having: a firstmagnetic layer whose direction of magnetization is substantially pinnedin one direction; a second magnetic layer whose direction ofmagnetization changes in response to an external magnetic field; anonmagnetic intermediate layer located between the first and secondmagnetic layers; and a film provided in the first magnetic layer, in thesecond magnetic layer, at an interface between the first magnetic layerand the nonmagnetic intermediate layer, or at an interface between thesecond magnetic layer and the nonmagnetic intermediate layer, the filmhaving a thickness not larger than 3 nanometers, and the film having atleast one selected from the group consisting of oxide, nitride,oxinitride, phosphide, and fluoride; and a pair of electrodeselectrically coupled to the magnetoresistance effect film and configuredto supply a sense current perpendicularly to a film plane of saidmagnetoresistance effect film.

According to other embodiment of the invention, there is provided amagnetic reproducing apparatus which reads information magneticallyrecorded in a magnetic recording medium, the magnetic reproducingapparatus comprising a magnetic head having a magnetoresistance effectelement including: a magnetoresistance effect film having: a firstmagnetic layer whose direction of magnetization is substantially pinnedin one direction; a second magnetic layer whose direction ofmagnetization changes in response to an external magnetic field; anonmagnetic intermediate layer located between the first and secondmagnetic layers; and a film provided in the first magnetic layer, in thesecond magnetic layer, at an interface between the first magnetic layerand the nonmagnetic intermediate layer, and/or at an interface betweenthe second magnetic layer and the nonmagnetic intermediate layer, andthe film having at least one selected from the group consisting ofoxide, nitride, oxinitride, phosphide, and fluoride; and a pair ofelectrodes electrically coupled to the magnetoresistance effect film tosupply a sense current perpendicularly to a film plane of saidmagnetoresistance effect film, wherein a product AR of an area A andresistance R is equal to or smaller than 500 mΩμm², where the area A isan area of a portion of the magnetoresistance effect film that the sensecurrent substantially passes through, and the resistance R is aresistance obtained between the pair of electrodes, or a resistance Rbetween the pair of electrodes is equal to or smaller than 100Ω.

According to other embodiment of the invention, there is provided amagnetic memory comprising a plurality of magnetoresistance effectelements arranged in a matrix fashion, the magnetoresistance effectelement including: a magnetoresistance effect film having: a firstmagnetic layer whose direction of magnetization is substantially pinnedin one direction; a second magnetic layer whose direction ofmagnetization changes in response to an external magnetic field; anonmagnetic intermediate layer located between the first and secondmagnetic layers; and a film provided in the first magnetic layer, in thesecond magnetic layer, at an interface between the first magnetic layerand the nonmagnetic intermediate layer, or at an interface between thesecond magnetic layer and the nonmagnetic intermediate layer, the filmhaving a thickness not larger than 3 nanometers, and the film having atleast one selected from the group consisting of oxide, nitride,oxinitride, phosphide, and fluoride; and a pair of electrodeselectrically coupled to the magnetoresistance effect film and configureto supply a sense current perpendicularly to a film plane of saidmagnetoresistance effect film.

According to other embodiment of the invention, there is provided amagnetic memory comprising a plurality of magnetoresistance effectelements arranged in a matrix fashion, the magnetoresistance effectelement including: a magnetoresistance effect film having: a firstmagnetic layer whose direction of magnetization is substantially pinnedin one direction; a second magnetic layer whose direction ofmagnetization changes in response to an external magnetic field; anonmagnetic intermediate layer located between the first and secondmagnetic layers; and a film provided in the first magnetic layer, in thesecond magnetic layer, at an interface between the first magnetic layerand the nonmagnetic intermediate layer, and/or at an interface betweenthe second magnetic layer and the nonmagnetic intermediate layer, andthe film having at least one selected from the group consisting ofoxide, nitride, oxinitride, phosphide, and fluoride; and a pair ofelectrodes electrically coupled to the magnetoresistance effect film tosupply a sense current perpendicularly to a film plane of saidmagnetoresistance effect film, wherein a product AR of an area A andresistance R is equal to or smaller than 500 mΩμm², where the area A isan area of a portion of the magnetoresistance effect film that the sensecurrent substantially passes through, and the resistance R is aresistance obtained between the pair of electrodes, or a resistance Rbetween the pair of electrodes is equal to or smaller than 100Ω.

According to embodiment of the invention, a magnetic field detectionwith a high sensitivity can be stably obtained and a magnetic headhaving a high output and high S/N even at a high recording density and amagnetic reproducing apparatus, and a magnetic memory of the degree ofhigh integration can be realized with low power consumption, and themerit on industry is great.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given here below and from the accompanying drawings of theembodiments of the invention. However, the drawings are not intended toimply limitation of the invention to a specific embodiment, but are forexplanation and understanding only.

In the drawings:

FIG. 1 is a schematic diagram for explaining the basic concept of theinvention;

FIG. 2A is a schematic diagram showing band structure of the usual halfmetal, and FIG. 2B is a schematic diagram showing band structureacquired by very thin oxide layer in the invention;

FIGS. 3A through 3C are conceptual diagrams for explaining a differencebetween a physical principle of CCP, and a physical principle of spinfiltering by a very thin oxide layer TB of the invention;

FIG. 4 is a principal part sectional view showing structure where anon-magnetic layer NM is provided in the upper and lower sides of thevery thin oxide layer TB;

FIG. 5 is a principal part sectional view which expresses a modificationof structure expressed to FIG. 4, and expresses structure where anon-magnetic layer NM of a very thin is inserted only in one side amongthe upper and lower sides of a very thin oxide layer TB;

FIG. 6 expresses a case where a very thin oxide layer TB is inserted inan interface of a pinned layer P (or a free layer F) and a spacer layerS;

FIG. 7 is a schematic diagram showing a structure where a very thinoxide layer TB is provided in the opposite side of a pinned layer P (ora free layer F) from the spacer layer S;

FIG. 8 expresses structure where a very thin oxide layer TB was insertedinto a pinned layer P (or a free layer F)

FIG. 9 is a schematic diagram showing structure where a very thinnon-magnetic layer NM and a metal magnetic layer FM are provided only inone of the upper and lower sides of a very thin oxide layer TB;

FIG. 10 illustrates structure where a very thin oxide layer TB isinserted in an interface of a pinned layer P (or a free layer F) and aspacer layer S;

FIG. 11 illustrates structure where a very thin oxide layer TB isinserted in an interface by the side of opposite as a spacer layer S ofa pinned layer P (or a free layer F);

FIG. 12 is a schematic diagram showing a case where portions beingunreacted (un-oxidized, un-nitrided, non-fluoridated) are contained in avery thin oxide layer TB;

FIG. 13 is a schematic diagram showing a case where unreacted metallicelements exist uniformly in a very thin oxide layer TB as the form notof granular but a more detailed cluster TBC;

FIGS. 14A through 14D are sectional schematic diagrams which illustrateinsertion locations of a very thin oxide layer TB;

FIGS. 15A through 15D are schematic diagrams which illustrate structureswhere a very thin oxide layer TB is inserted in both pinned layer P andfree layer F;

FIGS. 16A through 16D are schematic diagrams showing examples where avery thin oxide layer TB is inserted in an inside of a pinned layer P ora free layer F;

FIGS. 17A through 17D show the structures where the very thin oxidelayers TB are inserted in both a pinned layer P and a free layer F;

FIGS. 18A through 18D show the structures where the very thin oxidelayers TB are provided in both inside the bulk and near the interface ina pinned layer P or a free layer F;

FIGS. 19A through 19D show the structures where two or more very thinoxide layers TB are inserted in either a pinned layer P or a free layerF, in order to aim at interface dependence scattering and the bulkscattering effect, and to reinforce the bulk scattering effect;

FIGS. 20A through 20D express element structures which aimed at theinterface scattering effect in either a pinned layer P or a free layerF, and aimed at the bulk scattering effect by two or more very thinoxide layers TB in a layer of another side;

FIGS. 21A through 21D illustrate further structures where two or morevery thin oxide layers TB are inserted in order to aim at both theinterface scattering effect and the bulk scattering effect also ineither a pinned layer P or a free layer F, and to heighten the bulkscattering effect further in one of layers;

FIGS. 22A through 22C are schematic diagrams which illustrate laminatedconstitutions of magnetoresistance effect elements which can be used inthe invention;

FIGS. 23A and 23B are schematic diagrams which illustrate spin valvestructures where a pinning layer is provided;

FIG. 24 is a conceptual diagram showing an example of a formationapparatus which forms a magnetoresistance effect element containing avery thin oxide layer TB in the embodiment;

FIG. 25 is a sectional view of the magnetoresistance effect element cutin parallel to the medium facing surface P which is opposite to amagnetic recording medium (not shown);

FIG. 26 is a sectional view of the magnetic resistance effect elementcut in the perpendicular direction to the medium opposite side P;

FIG. 27 is a perspective view that shows outline configuration of thiskind of magnetic reproducing apparatus;

FIG. 28 is a perspective view of a magnetic head assembly at the distalend from an actuator arm 155 involved, which is viewed from the disk;

FIG. 29 is a conceptual diagram which exemplifies the matrix structureof the magnetic memory of the embodiment;

FIG. 30 is a conceptual diagram showing another example of the matrixstructure of the magnetic memory of the embodiment;

FIG. 31 is a conceptual diagram showing a principal part of the crosssectional structure of a magnetic memory according to an embodiment ofthe invention; and

FIG. 32 shows the A-A′ line sectional view.

DETAILED DESCRIPTION

Unlike a TMR element, a CPP element is excellent in a shot noise or ahigh frequency response. In a CPP element, in order to obtain sufficientoutput without causing element resistance increase, essential increasein MR rate of change is needed. For that purpose, it is required to usea half metal with a high rate of spin polarization for a pinned layer ora free layer, or for both a pinned layer and a free layer.

However, realization of a half metal with Tc (or Tn) beyond roomtemperature needed for actual application is difficult with theconventional half metal technology. That is, realization of a high MRrate of change near the room temperature is difficult.

Then, in the invention, a new material structure which shows half metalnature in a room temperature with the spin valve structure has beenexamined. If such completely new material structure is realized, a highMR rate of change can be realized. Therefore, a high AdR can berealized, without increasing the resistance. Then a magnetoresistanceeffect element showing a large resistance change dR and a large outputvoltage is realized. As the result, a magnetoresistance effect elementsuitable for a high-density recording, a magnetic head using it,magnetic reproducing apparatus (Hard Disk Drive etc.) that carries it,and MRAM having a large capacity can be offered.

All the half metal material studied now was material with low Tc.Conversely, there was a problem that the rate of spin polarization waslow in the case of the material which has a high Tc.

Although the rate of spin polarization is low, the following materialscan be mentioned as a material with high Tc:That is, iron (Fe), cobalt (Co) and nickel (Ni) which haveferromagnetism, and alloy materials which contain any these elements asa main component can be mentioned. These materials have a Tc of hundredsof degrees in centigrade, and have a very stable magnetism even at hightemperatures.

The inventors have considered whether the half metal characteristic isrealizable by using alloy materials which contain these elements as amain component. Such materials are based on a simple bcc (body centeredcubic) metal, fcc (face centered cubic) metal, or hcp (hexagonalclose-packed) metal.

The inventors have greatly converted the way of thinking from theconventional approach toward a half metal. And in order to enlarge therate of spin polarization of electronic conduction in materials havinghigh Tc, the invention has been made.

That is, as mentioned above, in the conventional approach for a halfmetal, it does not start from a laminated structure like a spin valvebut premised on the material which has half metal nature in a singlelayer. As a result, the creation of material which has a complicatedcrystal structure and low Tc has been studied, and the approach ofcreating spin valve structure like CPP or TMR was taken using thosematerials. That is, creating an artificial material was not performed.According to such a conventional approach, many problems arise asexplained above.

The inventors noted that half metal nature was a phenomenon resultingfrom band structure of a crystal. Then, the inventors resulted in aconclusion that half metal nature can be realized also in a hightemperature beyond room temperature even in a spin valve structure whichused the conventional high Tc metal material as a base by performingdelicate band modulations. Specifically, a very thin layer of an oxide,a nitride, an oxinitride, a phosphide, or a fluoride layer of athickness of about 0.2 nm-3 nm is inserted into a ferromagnetic layerhaving a high Tc. Thus, it was found out that MR rate of change of theCPP characteristic increased greatly, without causing a rise inresistance. It is thought that MR rate of change improved according tothe band modulation effect.

In research of the conventional half metal material in a complicatedcrystal structure, half metal nature is greatly lost near the interfacewhich changes crystal band structure. On the other hand, the inventionbases on the approach to use the conventional magnetic material of highTc, and to realize a half metal nature by using an interfacialphenomenon induced by the very thin oxide layer (or a nitride, anoxinitride, a phosphide, or a fluoride layer). In this case, since thematerial of high Tc is used from the beginning unlike the approach ofthe conventional half metal research, efforts to raise Tc areunnecessary.

In the specification, the very thin layers aiming at band modulationsuch as oxide, nitride, fluoride, etc. are called “a very thin oxidelayer TB.” However, also when it is called a very thin oxide layer TB,it may not be limited to an oxide layer but may include a nitride layer,an oxinitride layer, a phosphide layer, and a fluoride layer. It becomespossible to produce the artificial band modulation effect by a very thinoxide layer TB. Then, two or more layers are inserted into aferromagnetic layer, or a surprising band structural change is attainedby changing a lamination cycle etc. at variety. It becomes possible asthe result to create many artificial substances. Compared with theapproach which forms a complicated crystal structure which has been madeconventionally, many artificial substances can be far formed with arealistic means using the thin film formation technology which can bemass-produced.

First, material of a pinned layer and a free layer is explained. Forthis material, 3d transition metals which have sufficiently high(hundreds of degrees in centigrade) Tc can be used as a base.Specifically, magnetic metal material with Tc beyond room temperature,such as iron (Fe), cobalt (Co), nickel (nickel), these alloys, and thesealloys including still another element can be used as a base.

If such material is used as a base, a problem of Tc will completely belost. Usually, although there are few differences in density of statesof up spin electron and down spin electron in such materials, and thedifference is very small it cannot be called “half metal nature.” Thishas determined a limit of MR rate of change of the conventional CPP spinvalve stricture. That is, although a problem of Tc temperature wasremoved, a rate of spin polarization needs to be increased.

However, when inserting a very thin oxide layer into such commonmagnetic metal material, band structure of a magnetic metal near theoxide layer shows a big change. That is, it is expected easily that bandstructure changes greatly when oxygen or a nitrogen element combineswith metallic elements. However, if the usual metal oxide material isformed thickly, resistance in case an electron passes the layer at thetime of perpendicular current passing will become high. With the oxidein these comparatively thick films, it is expected simply that halfmetal nature cannot be realized.

Since it will become like a tunnel barrier if thickness of an oxidelayer aiming at band modulation becomes thick, the increase ofresistance is produced. However, band structure of a magnetic metalmaterial near the very thin oxide layer can be modulated, withoutcausing large increase of resistance, when thickness of the oxide layeris thin enough. Since high Tc magnetism metal material is used as a basewhen such a very thin oxide layer is used, half metal nature can beadvantageously realized even at room temperature.

FIG. 1 is a schematic diagram for explaining the basic concept of theinvention. As expressed in this figure, spin valve structure is based onlaminated structure where a spacer layer S is inserted between a pinnedlayer P and a free layer F. These pinned layer P and a free layer Fconsist of a ferromagnetic substance which used iron (Fe), cobalt (Co),nickel (nickel), or manganese (Mn) with high Tc or Tn as a base. In theinvention, a very thin oxide layer TB is inserted into a pinned layer Pand/or a free layer F which consists of these ferromagnetic substances.

Then, band structure changes near this very thin oxide layer TB, and arate of a spin polarization of a conduction electron which passes thatinterface improves rather than the conventional ferromagnetic substancematerial of high Tc or high Tn. Consequently, the half-metal-likecharacteristic is realized and MR rate of change of a CPP elementimproves. As band structure acquired here, it does not need to belimited by narrow definition like the conventional half metal. Thereason is explained below.

FIG. 2A is a schematic diagram showing band structure of the usual halfmetal, and FIG. 2B is a schematic diagram showing band structureacquired by very thin oxide layer in the invention.

Namely, in this figure (a) and (b), the vertical axis expresses theenergy, the left-hand side of the horizontal axis expresses the densityof states of the down spin electrons, and the right-hand side of thehorizontal axis express the density of states of the up spin electrons,respectively.

According to the definition of the conventional “half metal”, theconditions where density of states (DOS) exist in either an up spinelectron or a down spin electron correspond to a “half metal.” However,when pursuing half metal nature as the conduction characteristic, suchconditions are not necessarily required.

A model of DOS by definition of the conventional “half metal” is shownin FIG. 2A. In the case of an example expressed in this figure, onlydensity of states of an up spin electron exists, and density of statesof a down spin electron does not exist near the Fermi level.

Since only electrons near the Fermi level can contribute to conduction,only an up spin electrons can contribute to conduction and down spinelectrons cannot contribute it in this situation. For this reason, it iscalled a “half metal.”

Only from a viewpoint of such DOS, search of the half metal material byband calculation etc. has so far been performed. If this viewpoint ispersisted in, a half metal which uses iron (Fe), cobalt (Co), or nickel(nickel) as a base will not be proposed.

However, what is required for a CPP element is that a half metal natureis obtained when electrons are made to conduct. And in order to fillthis demand, severe conditions that one of DOS of a up spin electron ora down spin electron does not exist completely at the Fermi level arenot needed.

That is, as expressed in FIG. 2B, a spin polarization does not have tobe carried out completely. As shown in Table 1, in a CPP element, adifference of the Fermi speed of an up spin electron and a down spinelectron is required. If a difference of the Fermi speed of an up spinelectron and a down spin electron is large, a ratio of a conductionelectron contributed to conduction will spread more greatly than adifference of an up spin electron expected only from a viewpoint ofsimple DOS, and a down spin electron.

Since a difference of the Fermi speed of an up spin electron and a downspin electron will be effective as a difference of the second power ifit is converted into conduction, it appears as a very big effect (I. I.Main, Phys. Rev. Lett., 83 (7), 1999, p1427). When this effect is takeninto consideration, it turns out that a difference of DOS of an up spinelectron and a down spin electron near the Fermi level does notnecessarily need to be close to 100%. In other wards, a definition of ahalf metal from a viewpoint of the conventional DOS is a sufficientcondition, but if it thinks from a viewpoint of electronic conduction,it is not a necessary condition. By taking a difference of theelectronic Fermi speed into consideration, it becomes a necessarycondition.

However, material search of the half metal characteristic on bandcalculation taken into consideration to the Fermi speed was not made atall. Even if taken into consideration to a difference of the Fermi speedof an up spin and a down spin, in material which shows the conventionalhigh Tc, a half metal nature as conduction was not realized. MR rate ofchange in alloy material which used as a base simple iron (Fe), cobalt(Co), and nickel (nickel) investigated so far was remarkably lower thanMR rate of change which should be realized by half metal. That is, in aspin valve element using material which used the conventional high Tcferromagnetism material as a base, a certain means to change the Fermispeed was not considered at all.

On the other hand, the inventors noted that the Fermi speed alsooriginated in band structure of a crystal deeply. And it was discoveredthat conduction half metal nature was realized by producing bandmodulation in a magnetic material layer which used high Tc material as abase. Here, if an oxide or a nitride, oxinitride, phosphide, andfluoride are used, band modulation can be effectively produced by usingvery small quantity of them. Then, in order to acquire the bandmodulation effect, a very thin oxide layer TB by such material wasinvented.

In order not to raise resistance of an element, it must be made forthese very thin oxide layer TB to have to bring about the bandmodulation effect in the sufficiently thin state. Progress of filmformation technology in recent years can realize now creation of anartificial lattice of an oxide layer of such a very thin, or a nitridelayer.

When thought only on the conventional film formation technical level,such an artificial lattice was what cannot be realized at all.

This is also the cause as which an artificial substance which inserted avery thin oxide layer of such was not devised. An inventors was able toestablish technology which forms an oxide layer of a very thin into amagnetic material, and was able to result in a the invention based on aresult that these artificial substances' being formed and a rate of spinpolarization change a lot.

As an effect of a very thin oxide layer TB in the invention, asexplained above, as expressed in FIG. 2B, 100% polarization of DOS mustnot necessarily be realized and an effect which a difference produces atthe Fermi speed should just be acquired. The Fermi speed of an up spinelectron and a down spin electron is determined by situation of a Fermisurface. Therefore, if band structure changes with very thin oxidelayers TB, these Fermi speed will also change.

As explained above, in the invention, the band modulation effect isacquired by inserting a very thin oxide layer TB. This very thin oxidelayer TB can be formed with an oxide, a nitride, an oxinitride, thephosphide, or fluoride.

Here, the very thin oxide layer TB in the invention differs from afilter layer for resistance adjustment which is provided for mere“current constriction (CCP (Current Confined Path)) in respects of afunction and a physical principle.

Such a filter layer for resistance adjustment has pinholes of a certainrate. That is, it is the oxide layer (or a nitride layer, a fluoridelayer) which is not uniform. On the other hand, a very thin oxide layerTB of the invention has low resistance itself, or hardly causes aresistance rise for sufficiently thin thickness. It does not have a roleto adjust resistance with the ratio or area of pinholes, etc. In theinvention, it is not so preferred from a viewpoint of band modulationthat deviation of a current path comes out. As for a very thin oxidelayer TB in the invention, it is preferred that it is the uniform oxidelayer (or a nitride layer, a fluoride layer) which does not havepinholes.

Here, a “uniform” oxide layer shall mean that a pinhole average diameteris less than 20% to the sum of thickness of a free layer, a non-magneticspacer layer, and a pinned layer. As the measuring method, the TEM(transmission electron microscope) observation can be used, for example.As the manufacture method to form a uniform very thin oxide layer TB,the ion beam oxidizing method, a plasma oxidation method, the radicaloxidizing method, a high energy oxidization method using a gas clusterion beam, etc. can be used as will be mentioned later.

As for mean thickness of a very thin oxide layer TB, it is preferredthat it is the range of 0.2 nm-3 nm. Here, “mean thickness” is theaverage value when observing five points at intervals of 5 nm toward thedirection of a film plane. A sectional TEM photograph of an element etc.can be used for this measurement. A definition about this “meanthickness” shall be the same for each layer, such as non-magnetic layerNM, as will explained in full detail behind.

As the very thin oxide layer TB, if a layer made of oxide, nitride,oxinitride, phosphide or fluoride of thickness of an about 0.2 nm isprovided, sufficient effect will be obtained depending on selection of aproper material. By insertion of a uniform very thin oxide layer TB,since current flows uniformly, the spin filtering effect can also beexpected.

FIGS. 3A through 3C are conceptual diagrams for explaining a differencebetween a physical principle of CCP, and a physical principle of spinfiltering by a very thin oxide layer TB of the invention.

FIG. 3A shows a case where a very thin oxide layer TB is inserted in apinned layer P in the embodiment. FIG. 3B shows the structure where anoxide layer for CCP is inserted in a pinned layer P, and FIG. 3C showsthe structure where an oxide layer for CCP is inserted in a spacer layerS.

As shown in FIGS. 3B and 3C, since the oxide layer for CCP is providedfor a current constriction and for a filter for resistance adjustment,the thin current path CP is provided in the oxide layer.

When electrons pass the current path CP intermittently provided into theoxide layer, both an up spin electron US and a down spin DS pass thecurrent path CP. That is, a spin dependence effect is not produced. inthis case, a rise of MR rate of change is acquired according to aneffect of the current constriction.

For this current constriction purpose, the oxide layers for CCP aredivided into portions which passes current, and portions which blockcurrent, as shown in the figures.

On the other hand, in the case of a very thin oxide layer TB by theembodiment, the electronic spin filtering effect arises according to theband modulation effect. That is, the spin-depending conductioncharacteristic for which a down spin electrons DS are hard to passalthough the up spin electrons US easily pass, is obtained.

A large MR rate of change can be obtained according to an effect of spinfiltering, without raising resistance.

Hereafter, the embodiment of the invention will be explained, referringto the drawings.

In a the invention, as expressed in FIG. 1, by inserting a very thinoxide layer TB, a state of a pinned layer P and/or a free layer F can bechanged, and high MR rate of change and a high output signal can berealized. The very thin oxide layer TB can be inserted in the pinnedlayer and/or in the free layer and/or at the interfaces between theselayers and the spacer layer.

In the invention, a non-magnetic layer of a very thin may be insertedbetween the very thin oxide layer TB and the ferromagnetic layer.

FIG. 4 is a principal part sectional view showing structure where anon-magnetic layer NM is provided in the upper and lower sides of thevery thin oxide layer TB. That is, this figure expresses structure wherea very thin oxide layer TB is inserted into the pinned layer P or thefree layer F, and a very thin non-magnetic layer NM is further insertedfor both the upper and lower sides thereof.

Since thickness of this non-magnetic layer NM is thin enough, upper andlower parts of the ferromagnetic layer P (F) are magnetically coupled bysufficient strength via the very thin oxide layer TB and thenon-magnetic layer NM. A form of this magnetic coupling may be aferromagnetic coupling or a antiferromagnetic coupling. And in order toobtain sufficient magnetic coupling of upper and lower parts of theferromagnetic layer P (F), the very thin oxide layer TB and thenon-magnetic layer NM need to be both sufficiently thin. When the bandmodulation effect is aimed at, sufficient effect can be acquired even ifthe non-magnetic layer is made very thin.

Mean thickness of a very thin oxide layer TB is preferably from about0.2 nm to 3 nm. In order to prevent a degradation of the magneticcoupling between magnetic layers of the upper and lower sides, as forthickness of the non-magnetic layer NM, it is still more desirable thatit is from about 0.2 nm to 1 nm.

As for sum total thickness of a very thin oxide layer TB and anon-magnetic layer NM, it is desirable from 0.4 nm to 3 nm, and moredesirably from 0.4 nm to 2 nm. The reason is that magnetic coupling ofthe magnetic layers of the upper and lower sides through thenon-magnetic layer and the very thin oxide layer will become weak ifthickness of the non-magnetic NM becomes thick. That is, a non-magneticlayer NM in the embodiment is not aiming at an effect as a barrier layerfor making oxygen of a very thin oxide layer not touch a magnetic layerfrom a viewpoint of soft magnetism etc.

Material which is later mentioned about Table 5 as a material of a verythin oxide layer TB is desirable. As a material of the non-magneticlayer NM, aluminum (Al), copper (Cu), gold (Au), silver (Ag), ruthenium(Ru), rhodium (Rh), iridium (Ir), rhenium (Re), titanium (Ti), vanadium(V), chromium (Cr), manganese (Mn), magnesium (Mg), tantalum (Ta),tungsten (W), or hafnium (Hf) is desirable, and it is especiallydesirable to use copper (Cu), gold (Au), or silver (Ag).

Insertion of a non-magnetic metal layer NM of these very thins providesa metal layer other than a ferromagnetic layer in a thin oxide layer TBinterface. Therefore, the way of contribution of the band modulationeffect changes and the spin filtering effect becomes strong.

A loss of a spin memory of electrons which flow in a very thin oxidelayer TB from ferromagnetic layer P (F) etc. can be controlled byinserting a non-magnetic metal layer NM.

In any case, it becomes possible by providing a non-magnetic layer NM toenlarge further the increase effect of MR rate of change by a very thinoxide layer TB.

FIG. 5 is a principal part sectional view which expresses a modificationof structure expressed to FIG. 4, and expresses structure where anon-magnetic layer NM of a very thin is inserted only in one side amongthe upper and lower sides of a very thin oxide layer TB. Also in thisexample of transformation, it may be the same as that of what wasmentioned above about FIG. 4 about material, thickness, etc. of a verythin oxide layer TB and a very thin non-magnetic layer NM.

FIG. 6 expresses a case where a very thin oxide layer TB is inserted inan interface of a pinned layer P (or a free layer F) and a spacer layerS. Also in this case, a non-magnetic layer NM of a very thin can beprovided between a very thin oxide layer TB and a pinned layer P (a freelayer F). About the function, it is the same as that of what wasmentioned above about FIGS. 4 and 5.

FIG. 7 is a schematic diagram showing a structure where a very thinoxide layer TB is provided in the opposite side of a pinned layer P (ora free layer F) from the spacer layer S. It is the same as that of whatmentioned above about FIGS. 4 and 5 about that function also in thisstructure. In this case, since a magnetic layer does not necessarilyexist via a non-magnetic layer NM and a very thin oxide layer TB, themagnetic coupling between the upper and lower sides do not need to becared about. However, from a viewpoint of the band modulation effect,the desirable thickness range of a non-magnetic layer NM and a very thinoxide layer TB is the same as that of what has so far been shown.

In order to acquire an effect of the invention fully, the structurewhere a very thin oxide layer exists in a magnetic layer film, or thestructure where a very thin oxide layer exists in an interface with aspacer layer as shown in FIGS. 4 through 6 is more preferable than thestructure of FIG. 7 where a very thin oxide layer exists in a positionmost distant from the spacer layer S. Structures shown in FIGS. 8through 10 mentioned later are also more preferred than a structureshown in FIG. 11 by same reason. For example, as for a very thin oxidelayer, it is desirable to be located within 3 nm from a non-magneticspacer layer.

Moreover, the same effect is acquired by inserting the very thin oxidelayer in a pin layer or a free layer. It is more effective to insert ina pin layer at this time than to insert in a free layer. That is becausethe magnetization response of the free layer may fall on deviceoperation, when the very thin oxide layer is inserted in the interfaceor the inside of the free layer. In particular, this poses an essentialproblem, when providing the very thin non-magnetic layer NM in additionto the very thin oxide layer TB. And it becomes difficult to use it in

and a free layer.

FIGS. 8 through 11 are principal part sectional views which illustratestructures where a metal magnetic layer FM is further provided between avery thin non-magnetic layer NM and a very thin oxide layer TB.

First, FIG. 8 expresses structure where a very thin oxide layer TB wasinserted into a pinned layer P (or a free layer F). And a metal magneticlayer FM is laminated at the upper and lower sides of a very thin oxidelayer TB, and a ferromagnetic layer is further laminated at the outsidevia a very thin non-magnetic layer. By providing such a magnetic layerFM, as mentioned above about FIG. 4, material which adjoins a very thinoxide layer TB is made to be changed suitably, and the band modulationeffect of a very thin oxide layer TB can be emphasized.

In the case of this example, by inserting a metal magnetic layer FM, amagnetic effect in inside of a very thin oxide layer TB is assisted, andan effect which promotes magnetic coupling of a pinned layer P of theupper and lower sides through a very thin oxide layer TB (a free layerF) is acquired.

On the other hand, when a very thin oxide layer TB is formed byself-oxidization (or a self-nitride, self-fluoridation, etc.) of a metallayer, this metal magnetic layer FM may correspond to a portion whichremained as that non-oxidized portion. In such a case, a laminatedstructure of a very thin oxide layer TB and a metal magnetic layer FMcan be formed, keeping good the adjustment of an interface of a verythin oxide layer TB and a metal layer FM.

Next, FIG. 9 is a schematic diagram showing structure where a very thinnon-magnetic layer NM and a metal magnetic layer FM are provided only inone of the upper and lower sides of a very thin oxide layer TB. That is,a very thin oxide layer TB is inserted into a pinned layer P (or a freelayer F), and a metal magnetic layer FM and a non-magnetic layer NM arelaminated at the bottom. Also in this case, an effect mentioned aboveabout FIGS. 4 through FIG. 8 is acquired.

FIG. 10 illustrates structure where a very thin oxide layer TB isinserted in an interface of a pinned layer P (or a free layer F) and aspacer layer S. That is, the same effect as what was mentioned aboveabout FIGS. 4 through 9 is acquired by inserting a metal magnetic layerFM and a non-magnetic layer NM also in this case.

FIG. 11 illustrates structure where a very thin oxide layer TB isinserted in an interface by the side of opposite as a spacer layer S ofa pinned layer P (or a free layer F). The same effect as what wasmentioned above about FIGS. 4 through 9 is acquired by inserting a metalmagnetism layer FM and a non-magnetic layer NM also in this case. Inthis case, since a magnetic layer does not necessarily exist via anon-magnetic layer NM and a very thin oxide layer TB, magnetic couplingbetween the upper and lower sides do not need to be cared about.However, from a viewpoint of the band modulation effect, the desirablethickness ranges of a non-magnetic layer NM and a very thin oxide layerTB are the same as that of what has so far been shown.

On the other hand, although it is preferred that it is a uniform oxidefilm as for a very thin oxide layer TB used in the embodiment. However,it is not limited to this, and the oxide layer TB may not oxidizedcompletely. This is the same in the case of most fundamental structurethat does not contain a very thin non-magnetic layer NM as illustratedin FIG. 1.

FIG. 12 is a schematic diagram showing a case where portions beingunreacted (un-oxidized, un-nitrided, non-fluoridated) are contained in avery thin oxide layer TB. That is, in the case of an example of thisfigure, a very thin oxide layer TB has a reacted portion TBR in wheremetal have reacted (oxidization, a nitride, fluoridation, etc.), and aportions TBM where metal etc. remains in the unreacted state. Theunreacted portions TBM may exist in the form of a cluster, or in theform of granular, as illustrated in FIG. 12.

Thus, if the unreacted metal portions TBM are made to remain in a film,resistance of a conduction to pass electrons through the very thin oxidelayer TB perpendicularly can be reduced.

When a very thin oxide layer TB consists of oxides (or a nitride,fluoride, etc.) of a magnetic element, those which remain in a film asunreacted metallic elements (TBM) is a magnetic element. In this case,it is effective in maintaining magnetism in a very thin oxide layer TB,and an effect of helping magnetic coupling of a magnetic layers of theupper and lower sides through a very thin oxide layer TB is acquired.

When metallic elements remain, current tends to flow the unreactedportions TBM preferentially. In this case, if the remaining metalelement is a magnetic metal which is surrounded by the reacted portionTBR, increase of the spin filtering effect may arise, and MR rate ofchange may increase further.

As magnetic metallic elements which are easy to remain in the unreactedstate in the very thin oxide layer TB, iron (Fe), cobalt (Co), nickel(nickel), etc. can be mentioned. Especially among these, since cobalt(Co) cannot oxidize most easily, in forming a very thin oxide layer TBby oxidation reaction, cobalt (Co) tends to remain in an unreacted metalstate. As an element which constitutes a part for such an unreactedmetal portions TBM, non-magnetic metallic elements, such as copper (Cu),gold (Au), silver (Ag), a ruthenium (Ru), rhodium (Rh), and rhenium(Re), can also be mentioned.

FIG. 13 is a schematic diagram showing a case where unreacted metallicelements exist uniformly in a very thin oxide layer TB as the form notof granular but a more detailed cluster TBC. Thus, also when unreactedmetallic elements are uniformly distributed in a very thin oxide layerTB by the shape of a detailed cluster, an effect homogeneous as what wasmentioned above about FIG. 12 can also be expected. About a kind ofmetallic elements which are easy to form a cluster TBC of an unreactedstate, it is the same as that of what was mentioned above about FIG. 12.

FIGS. 14A through 14D are sectional schematic diagrams which illustrateinsertion locations of a very thin oxide layer TB. That is, FIGS. 4A and4C express examples where a very thin oxide layer TB is inserted nearthe interface with a spacer layer S of a free layer F or a pinned layerP, respectively. In this case, spin-dependent interface scattering willcontribute to improvement in MR rate of change greatly. By providing avery thin oxide layer TB, band structure of a magnetic layer F (or P)which is in contact with a spacer layer S changes. And when an electronwhich contributes to conduction carries out spin polarization greatly toeither a up or a down state, MR rate of change improves.

When based on interface scattering, effect for a ferromagnetic layer F(or P) which is in contact with a spacer layer S with the sufficientband modulation effect by a very thin oxide layer TB must be given. Forthis reason, as for thickness T of a ferromagnetic layer between a verythin oxide layer TB and a spacer layer S, it is preferred not to becomenot much thick. When thickness T is 1 nm or less, the “interface effect”is acquired near the interface with a spacer layer S which is expressedin FIGS. 14A through 14D. On the other hand, when it is inserted in aninside of a magnetic layer, the “bulk scattering effect” is acquired aswill be explained later with reference to FIG. 16.

As the thinnest limit, the structures where the very thin oxide layer TBis inserted in an interface of a pinned layer P or a free layer F, and aspacer layer S, are shown in FIGS. 14B and 14D, as cases of thickness Tof 0 nm. An effect which modulates the band structure of not only thepinned layer P and/or the free layer F but also the spacer layer S canbe obtained in these cases, and the modulation effect may become moreremarkable depending on material of the spacer layer S.

FIGS. 15A through 15D are schematic diagrams which illustrate structureswhere a very thin oxide layer TB is inserted in both pinned layer P andfree layer F. Since the interface effect by band modulation arises intwo locations in the element in the case of these examples, the riseeffect of MR rate of change will improve further.

A very thin oxide layer TB may be inserted not only at the interface ofa pinned layer P or a free layer F, and a spacer layer S but also insideof the pinned layer P or the free layer F. Thus, a half metal natureinside the pinned layer P and/or the free layer F may be emphasized.

FIGS. 16A through 16D are schematic diagrams showing examples where avery thin oxide layer TB is inserted in an inside of a pinned layer P ora free layer F.

That is, FIGS. 16A and 16B express examples where a very thin oxidelayer TB is inserted in an inside of a pinned layer P or a free layer F.

In this case, it is possible to produce the spin dependence bulkscattering effect inside a pinned layer P or a free layer F. In order topull out this effect still more notably, a two or more very thin oxidelayer TB can be inserted into the magnetic layer.

FIGS. 16C and 16D express examples where two or more very thin oxidelayers TB are inserted in this way. In this case, it is desirable toinsert in the ferromagnetic layers by making an interval of very thinoxide layers TB into about 0.2 nm to 3 nm. Since band structure willchange with the interval and the period of the very thin oxide layersTB, half metal nature, i.e., MR rate of change, will change. Any numberof laminations of the very thin oxide layers TB in a pinned layer P anda free layer F may be adopted. Actually, about two layers to fifteenlayers are desirable.

As illustrated in FIGS. 17A through 17D, when the very thin oxide layersTB are inserted in both a pinned layer P and a free layer F, an effectof half metal nature improves further.

As illustrated in FIGS. 18A through 18D, the very thin oxide layers TBmay be provided in both inside the bulk and near the interface in apinned layer P or a free layer F.

In this case, the spin-dependent interface scattering effect (FIGS. 14and 15) in a spacer layer interface, and the spin-dependent bulkscattering effect (FIGS. 16 and 17) inside a pinned layer P or freelayer F, are both acquired, and even higher MR rate of change can beexpected.

Supposing half metal nature in an interface is in a perfect ideal state,scattering of either an up spin electron or a down spin electron will becarried out 100% (all) by the interface. Therefore, combination with thebulk scattering effect should not have a meaning. However, it isdifficult to realize a completely ideal state with an actual element inmany cases. Therefore, the further improvement in MR rate of change canbe desired by the addition of half metal nature within the bulk.

FIGS. 18A through 18D express element structures of a pinned layer P ora free layer F which is for acquiring interface dependence scatteringand the bulk scattering effect only in one side either.

On the other hand, FIGS. 19A through 19D show the structures where twoor more very thin oxide layers TB are inserted in either a pinned layerP or a free layer F, in order to aim at interface dependence scatteringand the bulk scattering effect, and to reinforce the bulk scatteringeffect.

FIGS. 20A through 2D express element structures which aimed at theinterface scattering effect in either a pinned layer P or a free layerF, and aimed at the bulk scattering effect by two or more very thinoxide layers TB in a layer of another side.

FIGS. 21A through 21D illustrate further structures where two or morevery thin oxide layers TB are inserted in order to aim at both theinterface scattering effect and the bulk scattering effect also ineither a pinned layer P or a free layer F, and to heighten the bulkscattering effect further in one of layers.

The invention is not limited to combination illustrated in FIGS. 14Athrough 21D. Based on these views, various combinations where a verythin oxide layer TB is inserted in a pinned layer P and a free layer Fcan be considered freely.

When providing two or more layers of very thin oxide layers TB, materialof these very thin oxide layers may be the same kind, or materials ofthese layers TB may be mutually different.

Easiest spin valve structures were illustrated in FIGS. 14A through 21D.However, with the application of the invention, the same function effectcan be acquired in various kinds of other element structures.

FIGS. 22A through 22C are schematic diagrams which illustrate laminatedconstitutions of magnetoresistance effect elements which can be used inthe invention.

That is, an example expressed in FIG. 22A is the spin valve structure ofthe so-called “bottom type” where a pinned layer P is provided in thebottom (side near a substrate which is not illustrated).

FIG. 22B is the spin valve structure of the so-called “top type” where apinned layer P is provided in the top (side far from a substrate whichis not illustrated).

FIG. 22C expresses a spin valve structure of the so-called “dual spinvalve type” where pinned layers P are provided in the upper and lowersides of a free layer F via a spacer layer S, respectively.

The invention can be applied to any these element structures, and canacquire the same effect. The invention is applicable also to an elementof structure like an “artificial lattice type” where three or morelayers for example, of spacer layers established besides these. That is,also in these element structures, a function of a very thin oxide layerTB is the same as that of what was illustrated to FIGS. 14A through 21D.

By the way, in spin valve structure, the direction of magnetization of afree layer F changes to an external magnetic field. In contrast to this,about a pinned layer P, it is preferable to provide a pinning layer foradhering the magnetization direction of the pinned layer so that themagnetization direction may not change to an external magnetic field.

FIGS. 23A and 23B are schematic diagrams which illustrate spin valvestructures where a pinning layer is provided. That is, as expressed inFIG. 23A, the magnetization direction of a pinned layer P can bedirectly adhered with an antiferromagnetic film AF or a hard magneticfilm HM. Alternatively, as expressed in FIG. 23B, so-called “syntheticstructure” may be adopted.

In synthesizer tick structure, the magnetization of the ferromagneticlayer FM is fixed by the antiferromagnetic film AF, and via theantiferromagnetic coupling film AC which consists of ruthenium (Ru)etc., it is coupled to the pinned layer P in antiferromagnetic fashion,so that the magnetization of the pinned layer p is fixed.

In the invention, any pinning means illustrated in FIGS. 23A and 23B canbe used. On the other hand, as a concrete material of a very thin oxidelayer TB, an oxide or a nitride which is easy to cause band changegreatly can be mentioned. In this case, an oxide layer or a nitridelayer containing 3d transition metal which is easy to cause band changeis especially preferred as the material of the very thin layer.

Specifically, the oxide, nitride, oxinitride, phosphide, or fluoride ofan element, such as calcium (calcium), scandium (Sc), titanium (Ti),vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co),nickel (nickel), copper (Cu), strontium (Sr), yttrium (Y), barium (Ba),lantern (La), hafnium (Hf), and tungsten (W) can be mentioned. Alsoexcept these, an oxide or nitrides of an element such as zinc (Zn),zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium(Rh), palladium (Pd), tantalum (Ta), iridium (Ir), and platinum (Pt) canalso be used.

Except iron oxide (Fe₃O₄), all oxides and nitrides of these elementswere thought not to show a half metal nature so far.

In the case of iron oxide (Fe₃O₄), in order to realize thebulk-characteristic as Fe₃O₄ material, thickness more than one unit cellwas needed in the state of spinal structure. On the other hand, in thecase of an iron oxide, in the invention, it is not necessary to havespinel structure. In the invention, a very thin film of 1 through 5 monolayers (atomic layers) may be sufficient to obtain the effect. At such athickness range, it is difficult to define the spinel structure. Even ifthe thickness is larger than 5 mono layers, it may be used as long asthe resistance is kept low. Actually, it may be allowable if thethickness of less than 10 mono layers. In order to obtain a lowerresistance, it is desirable to make the thickness not exceeding 5 monolayers.

The term “a mono layer (atomic layer)” means the number of existinglayers of oxygen, nitrogen, phosphorous and fluoride which exists in thedirection of thickness, when the film is observed from the film section.It is defined as average mono thickness by average value of mono layerthickness measured about five points at intervals of 5 nm. A sectionalTEM of an element can be used as a concrete observation means. If thesecompounds are crystalline, the atomic layers can be counted on thelattice image of TEM.

Conventionally, an oxide, a nitride, and fluoride with sufficientperiodic structure were inserted. On the other hand, in a the invention,it is possible to obtain the effect by using a layer of an oxide, anitride, a phosphide, or a fluoride whose mean thickness is below 2 unitcell, and even in the case of mean thickness below 1 unit cell, forexample.

In the invention, the very thin oxide layer TB itself is not necessarilymade to produce half metal nature, as mentioned above.

In the invention, a ferromagnetic layer (a pinned layer P or a freelayer F) of high Tc which is in contact with a very thin oxide layer TBis made to produce half metal nature. Therefore, in the invention, aneffect is acquired by using a very thin layer. When it aims atresistance adjustment or a current constriction, a sufficient effectcannot be acquired by using such a very thin layer.

Since the invention aims at the band modulation effect in aferromagnetic layer (a pinned layer P, a free layer F), withoutproducing a rise of resistance, the oxide layer (or nitride layer) needto be formed in a sufficient thin thickness which does not bring aboutthe resistance rise effect.

Specifically, the thickness is desirably 0.2 nm to 1 nm. Even if thick,it is 2 nm or less, and it is required to be 3 nm or less as thegreatest tolerance level according to material.

Iridium (Ir), platinum (Pt), etc. with a large atomic number tend toproduce a spin orbital interaction among elements used as a very thinoxide layer TB. Therefore, since a spin memory loss arises, it is notdesirable.

On the other hand, element resistance AR of a CPP element is need to beless than 500 mΩμm², and preferably lower than 300 mΩμm², and is thehigh integration is aimed at, it is preferably lower than 200 mΩμm².When computing AR from an actual element, AR is computed as amultiplication of an effective area A of a current passing portion of aspin valve film and a resistance R of a CPP element.

Here, element resistance R can be determined by a direct measurementcalculation from the magnetoresistance effect element.

On the other hand, an effective area A of a current passing portion of aspin valve film is the quantity depending on the shape of themagnetoresistance effect element. For example, when the whole spin valvefilm is specified as an area which carries out sensing effectually,element area of the whole spin valve film can be specified as an currentpassing area A of a spin valve film. In this case, element area of aspin valve film should have become equal to or less than 0.09 μm² from aviewpoint of moderate element resistance.

However, area of an electrode which is in contact with the upper andlower sides of a spin valve film prescribes the current passingeffective area of a spin valve film, and when the pattering of the spinvalve film is not carried out, area of an electrode of the top of bottommay be the current passing area. When areas of the upper and lowerelectrodes are different, area of an electrode of the smaller one maydefine the effective area. In this case, element area of a spin valvefilm should have become also equal to or less than 0.09 μm² from aviewpoint of moderate element resistance.

It may not be easy to determine a strict current passing area dependingon the element structure or form of the electrodes. In thisspecification, a contact area of an electrode of the one where a contactarea is smaller is adopted as the current passing effective area A amongupper and lower electrodes.

In the invention, 100 ohms or less are realizable as a value of rawresistance R between electrodes of a magnetoresistance effect element.If this is not a magnetoresistance effect element by the invention, itis not easily to realize this resistance. Resistance here is the valueof resistance between 2 terminals of an electrode pad reproductionelement part of a head which is equipped at the tip of HGA (Head GimbalAssembly) in the case of a head.

Hereafter, the embodiment of the invention will be explained in moredetail referring to the examples.

FIRST EXAMPLE

The magnetoresistance effect element which has the following laminatedstructure was formed as the first example of the invention.

A lower electrode/tantalum (Ta) 3 nm/nickel iron chromium (NiFeCr) 5nm/platinum manganese (PtMn) 10 nm/cobalt iron (CoFe) 4 nm/ruthenium(Ru) 0.9 nm/cobalt iron (CoFe) [4 nm/very thin oxide layer 0.5 nm/cobaltiron (CoFe) 1 nm/copper (Cu) 5 nm/cobalt iron (CoFe) 1 nm/nickel ironcobalt (NiFeCo)/copper (Cu) 1 nm/tantalum (Ta)5 nm/upper electrode.

This example has structure where a very thin oxide layer TB is providedonly near the interface with a spacer layer S of a pinned layer P, asshown in FIG. 14C.

In a case of this structure, 100 mΩμm² to 200 mΩμm² is obtained as AR,and 5 mΩμm² to 30 mΩμm² is obtained as AdR. Moreover, if the AR riseeffect by the current constriction is combined, 500 mΩμm² may beobtained as AR and 25 mΩμm² to 150 mΩμm² may be obtained as AdR, as willbe explained later.

If a very thin oxide layer TB is inserted not only near the interfacewith a spacer layer S, but also into the pinned layer P and thus, thebulk scattering effect is used, about 1.5 times to 10 times of theabove-mentioned value can be obtained. Further, an effect of being 1.5times to 10 times many is acquired by inserting a very thin oxide layerTB in an interface between a free layer F and a spacer layer S.

Here, tantalum (Ta) 3 mm/nickel iron chromium (NiFeCr) 5 nm are the baselayers which served both as the buffer effect and the seed effect. As amaterial with a buffer effect like tantalum (Ta), titanium (Ti),zirconium (Zr), hafnium (Hf), vanadium (V), chromium (Cr), molybdenum(Mo), tungsten (W), and those alloy material may be used instead oftantalum (Ta).

An oxide or a nitride of such metals may be used. In this case, it isnot preferred that resistance goes up as CPP structure. Therefore, inthe case of an oxide, it is desirable to make it a very thin layer 2 nmor less. In the case of a nitride, it is desirable to make it aconductive nitride of low resistance, or to make it a very thin layer 2nm or less, when its resistance is high.

Concentration of chromium (Cr) in nickel iron chromium (NiFeCr) can bemade into about 0-40%. fcc metal, hcp metal, etc. can also be usedinstead of nickel iron chromium (NiFeCr).

For example, copper (Cu), zirconium (Zr), ruthenium (Ru), rhodium (Rh),palladium (Pd), silver (Ag), nickel (nickel), cobalt (Co), platinum(Pt), gold (Au), osmium (Os), rhenium (Re), and those alloy material canbe used.

As thickness of these base layers, 3 nm-10 nm or less is desirable.Material with seed effects other than such material can also be used.Since AdR of CPP changes with the crystalline differences arising from abase layer, material selection of a base layer is important, as will beexplained in more detail later.

Table 2 shows the examples of a base layer. Here, in the case of theso-called “top type” with which a pinned layer P is provided in the topfrom a free layer F, a base layer which has an oxide layer for currentconstriction effect may be used. CPP resistance can be adjusted byconstricting the current which flows the so-called spin dependencescattering unit (important unit of three layers which brings about MRchange) of a pinned layer P, a spacer layer S, and a free layer F.Simultaneously, though MR rate of change is same level, AdR can beincreased by increasing A. When storage density is not so high, it maybe used as a means to raise resistance.

Platinum manganese (PtMn) currently formed on a base layer isantiferromagnetic material, and is used to fix the magnetizationdirection of a magnetic layer formed on it. Instead of platinummanganese (PtMn), a gamma-Mn system antiferromagnetic film of a(manganese Mn) rich system, such as palladium platinum manganese(PdPtMn), iridium manganese (IrMn), and ruthenium rhodium manganese(RuRhMn) may be used. As thickness of this antiferromagnetic layer, 5nm-20 nm is desirable, and it is still more desirable that it is withina range of 7 nm-15 nm.

The cobalt iron (CoFe) 4 nm/ruthenium (Ru) 0.9 nm/cobalt iron (CoFe) 4nm/very thin oxide layer 0.5 nm/cobalt iron (CoFe) 1 nm/on theantiferromagnetic layer are pinned layer P. Here, the lower platinummanganese (PtMn) 10 nm/cobalt iron (CoFe) 4 nm/ruthenium (Ru) 0.9 nm aremade to call a pinning layer to fix the magnetization of the pinnedlayer P. In the example, “synthetic structure” where the magnetizationdirections cancel mutually via a ruthenium (Ru) is adopted.

The so-called “single layer pin structure” where cobalt iron (CoFe) 4nm/ruthenium (Ru) 0.9 nm is removed is also employable instead ofsynthetic structure. However, the synthetic structure is more desirable.In the case of synthetic structure, the fixed unidirectional magneticfield is large. Since the magnetization direction through a ruthenium(Ru) is reverse in the case of synthetic structure, a net magneticmoment which contributes to a disclosure magnetic field to the filmexterior is small, and thus it is advantageous on device operation. Inthe case of synthetic structure, as a magnetic layer between anantiferromagnetic film and a ruthenium (Ru), alloy material, such asiron cobalt (FeCo), nickel iron (NiFe), iron (Fe), cobalt (Co), andnickel (nickel), can be used besides cobalt iron (CoFe).

Moreover, the magnetization adherence method of having used hardferromagnetism films other than the magnetization adherence directionusing an antiferromagnetic film, such as CoPt and CoPtCr, can be used.In this case, a hard ferromagnetic film can be used instead of PtMn. Ora hard ferromagnetic film can be used instead of synthesizer tickstructure. When the magnetization is fixed by using a hard ferromagneticfilm, the merit that resistance of an element can be lowered isobtained. That is, compared with a metal film of comparatively highresistance like PtMn, CoPt is low resistance. It becomes possible toreduce the excessive resistance between upper and lower electrodes, andMR rate of change can be raised.

In the case of synthetic structure, the thickness of a magnetic layer(here CoFe4) between a ruthenium (Ru) and platinum manganese (PtMn) isdesirably to have little asymmetry with magnetic thickness(saturation-magnetization×thickness: Bsxt [T nm]) of the pinned layer Pformed on a ruthenium (Ru) (if the magnetic thickness is almost equal).This is because H_(uaflat) can be enlarged.

H_(uaflat) is the size of a magnetic field at which magnetizationpinning of a pinned layer can maintain its magnetization, when amagnetic field is impressed to an opposite direction to themagnetization pinned direction of the pinned layer. In this case,magnetization of a free layer is easily suitable in the magnetic fieldimpression direction in a lower field. Therefore, H_(uaflat) may be thestrength at which a relation of the magnetization directions of a freelayer and a pinned layer can maintain an anti-parallel state (highresistance state of a spin valve).

Here, in a resistance-magnetic field curve, a place where a decrease in3% from the greatest high resistance state occurs is defined asH_(uaflat). In order to enlarge contribution of spin dependencescattering, the thickness of the pinned layer P is preferably madethicker. However, since magnetization pinning by the PtMn becomes weakin this case, therefore, there is a limit in a thickness of the pinnedlayer P.

In order to obtain H_(uaflat) which satisfies the above tworequirements, and having a level at which satisfactory head operation isensured, the magnetic thickness of a magnetic layer between theantiferromagnetic layer and ruthenium (Ru) is preferably from 4 T nm to12 T nm, and more preferably from 6 T nm to 10 T nm.

The physical thickness at that time will change by Bs of a magneticlayer, however, is preferably in a range or 2 nm-6 nm, and morepreferably in a range of 3-5 nm.

Table 3 shows examples of the pinning layer.

The cobalt iron (CoFe) 4 nm/very thin oxide layer 0.5 nm/cobalt iron(CoFe) 1 nm/on the ruthenium (Ru) layer is the pinned layer P, whichdirectly contributes to the MR ratio.

In the case of the conventional magnetoresistance effect element, apinned layer was formed only of a metal layer of a simple cobalt iron(CoFe) layer, and a nickel iron (NiFe) layer, nickel iron cobalt (NiFeColayer) and an iron cobalt (FeCo) layer. On the other hand, in thisexample, a very thin oxide layer is provided between two cobalt iron(CoFe) layers.

Table 4 shows a typical material of a pinned layer P to which the verythin oxide layer TB is inserted. That is, it is possible to use not onlycobalt iron (CoFe) but also various kinds of laminated structures whichare listed on Table 4. A formation method of a very thin oxide layer TBwill be explained in full detail behind, referring to FIG. 24.

Table 5 shows examples of concrete materials of the very thin oxidelayer TB. The band modulation effect is acquired by using an oxide, anitride, a oxinitride, a phosphide, or a fluoride which contains atleast one of the elements which are listed on Table 5, as the materialof a very thin oxide layer TB. If an oxide with which at least onecontains 3d transition metal elements, such as Ti, Cr, V, Mn, Fe, Co,nickel, and Cu, also in it, and an oxide which contains at least oneelement among Al, Si, and Mg is used, it is easily compatible in aneffect of band modulation, and an effect of low resistance.

Ta, Zr, Hf, Zn, etc. are also desirable material for the very thin oxidelayer TB. As for the thickness of the layer TB, since it is notdesirable to raise resistance, it is preferably in a range of 0.2 nm-3nm, and more preferably in a range of 0.2 nm-2 nm, and still morepreferably in a range of 0.5 nm-1 nm. When thickness of a very thinoxide layer is comparatively as thick as 2-3 nm, in order not to raiseresistance, the inside of a very thin oxide layer does not oxidized,nitrided or oxinitrided completely, and it may be desirable that theyare the phosphide or fluoride.

When very thin oxide layers are 2-3 nm, comparatively thick oxide,nitride, or oxinitride layer, it is desirable to have an element whichremains into a very thin oxide layer with a metal state combined neitherwith oxygen nor nitrogen (element in the state where it has not combinedwith oxygen or nitrogen). In this case, it is because a rise ofresistance is not caused even if thickness is thick.

In this case, it is desirable that Co remains in the very thin oxidelayer with a metal state. When Co remains, the magnetic coupling of theupper and lower sides through a very thin oxide layer inside of a pinnedlayer or a free layer can be kept good, even if the thickness of a verythin oxide layer is comparatively thick.

It is more desirable for a two or more layers of thin very thin oxidelayers to exist rather than a very thin oxide layer of a comparativelythick single layer exists in a magnetic layer. Especially this isbecause the bulk scattering effect by spin filtering in a magnetic layerwhich carried out spin dependence can be acquired without raisingresistance. When it aims at the bulk scattering effect in the pinnedlayer or the free layer, it is especially preferred to have a 2-6 layersof very thin oxide layers TB. However, when providing a single very thinoxide layer for spin-dependent interface scattering, even a single layermay exhibit a greatest effect.

As concrete experiment data, the data of the element where a singlelayer of the very thin oxide layers was inserted into the pin layer isshown below.

When a very thin oxide layer is 0.5 nm in thickness, AR was about 200mΩμm². The MR rate of change when the main element which constitutes avery thin oxide layer is changed are as follows.

In the case of Co, it was 5%. In the case of nickel, it was 2.5%. In thecase of Fe, it was 15%. In the case of aluminum, it was 10%. In the caseof Ti, it was 11%. In the case of Cr, it was 8%. In the case of V, itwas 12%. In the case of Zr, it was 13%. In the case of Mo, it was 12%.In the case of Hf, it was 14%. In the case of Ta, it was 14%.

It is more advantageous to insert in a pin layer rather than a freelayer, when inserting a very thin oxide layer, as mentioned above.

It is for preventing the degradation of the response to the mediummagnetic field of a free layer. It becomes still more remarkable whenthe very thin non-magnetic layer NM is used together.

In a free layer, when the very thin non-magnetic layer NM is usedtogether, at least 1 nm or more of thickness of the magnetic layer ofeach top and bottom through the very thin oxide layer TM and the verythin non-magnetic layer NM is required, and more desirably 2 nm or moreis required.

Moreover, as mentioned above, when inserting a single very thin oxidelayer into a pin layer, the increasing rate of MR may depend on thepositions to insert. For example, in the first example mentioned above,instead of the pin structure having 4 nm (CoFe)/0.5 nm of very thinoxide layer/1 nm (CoFe), a structure of 2 nm (CoFe)/0.5 nm of very thinoxide layer/2 nm (CoFe) can be used. In this alternative structure, MRratio may decrease, since the very thin oxide layer becomes more remotefrom the space layer.

When the main element of a very thin oxide was Hf, specifically, MR rateof change of the structure of the first example was 14%. On the otherhand, in the case of 2 nm (CoFe)/0.5 nm of very thin oxide layer/2 nm(CoFe), MR rate of change falls down to 10%.

The same phenomenon was observed in the case where Co was used as themain element of the very thin oxide layer. That is, as the very thinoxide layer becomes closer to the space layer, the MR rate becomeslarger. That is, the structures as shown in FIG. 16C and FIG. 16D aremore desirable than structure as shown in FIG. 18A. As for the insertionpoint of the very thin oxide layer, specifically, it is desirable to setit as the range of less than 2 nm from a spacer layer. It is moredesirable to be within 1 nm from a spacer layer. It is the same evenwhen a very thin oxide layer is inserted in a free layer. That is, it isdesirable that a very thin oxide layer exists within 2 nm from a spacerlayer, and more desirable that the layer is within 1 nm place from thespacer layer.

When it is insufficient to insert a single very thin oxide layer nearthe spacer layer, two or more layers very thin oxide layers can beinserted to obtain further improvement. By inserting a very thin oxidelayer also in the place separated from the spacer layer rather than 2nm, MR rate of change goes up further. When inserting two or more verythin oxide layers, the material of each very thin oxide layer can bechanged. However, when the main element used as the mother material of avery thin oxide layer is not a non-magnetic element but a magneticelement like Fe and nickel, even if it is inserted in the placeseparated from the spacer layer rather than 2 nm, the effect ofsufficient MR rise may be demonstrated.

In the first example mentioned above, the thickness range from which thethickness of a very thin oxide layer becomes the optimal according toRA. For example, when the main element which constitutes a very thinoxide layer is Hf and thickness is 0.5 nm, RA is 200 mΩμm², and MR rateof change is 14%. When the thickness of a very thin oxide layer is 0.2nm, RA is 150 mΩμm² and MR rate of change is 10%. When the thickness ofa very thin oxide layer is 1 nm, RA is 250 mΩμm², and MR rate of changeis 14%.

When the thickness of a very thin oxide layer is 2 nm, RA is 300 mΩμm²and MR rate of change is 14%. When the thickness of a very thin oxidelayer is 3 nm, RA is 500 mΩμm² and MR rates of change was 10%.

If the very thin oxide layer becomes thicker, RA becomes larger. On theother hand, if the thickness of a very thin oxide layer becomes thick,MR becomes also larger. However, if a very thin oxide layer becomesthick too much, MR rate of change may fall.

The existence of such a very thin oxide layer can be observed by asection TEM (Transmission Electron Microscopy). When very thin oxidelayers are an oxide layer, a nitride layer, and an acid nitride layer,thickness can be discriminated from contrast of a section TEM. Whendiscernment of thickness is difficult, it is also possible to determinethe thickness by EDX (Energy Dispersive X-ray spectroscopy) analysiswhich extracted a diameter of a beam to about 1 nm. In this case, it isalso possible to calculate from a half width of the concentrationdistribution, of oxygen nitrogen, phosphorous, or fluorine while settingthe measurement points at intervals of 0.5 nm-1 nm in the film growthdirection, and plotting element distribution to a measurement positions.

When a very thin oxide layer consists of oxide or oxinitride, it is mostpreferred that the high Tc material located upper and lower side is Coor contains Co or Co. As a second choice, nickel or its alloy arepreferable, then as a third choice, iron or its alloy are preferable.This is because Co is most hard to oxidize and Ni is harder to oxidizethan iron. By preventing oxidization, the steep nature of an interfacewith a very thin oxide layer can be held, and diffusion of oxygen can beprevented. A structure element of a magnetic material which exists inthe upper and lower sides of a very thin oxide layer is discriminablewith the nano-EDX scan of a sectional TEM sample etc.

When a very thin oxide layer consists of an oxide layer or an acidnitride layer, as for a very thin oxide layer, it is desirable toinclude material which combines with oxygen stably, and especially atleast one element among Al, Si, Mg, Ti, V, Cr, Mn, Fe, Ta, Zr, Hf, and Wis preferred.

In order to form a stable oxide layer or a stable nitride layer, highenergy oxidization or a high energy nitride process which are mentionedlater are preferred. In that case, when Ar ion beam is used, Ar iscontained in the very thin oxide layer in a relatively higherconcentration. This content Ar may add a secondary effect to an effectof a very thin oxide layer. In order to acquire such secondary effect,it is desirable for a very thin oxide layer TB to contain Ar more thantwice, more desirably three times, compared with the magnetic layers ofits upper and lower sides.

A copper (Cu) layer on the pinned layer P is a non-magnetic spacer layerS which divides the pinned layer P and the free layer F magnetically.Instead of copper (Cu), gold (Au), silver (Ag), a ruthenium (Ru),rhodium (Rh), palladium (Pd), etc. can also be used. It is needed thatthickness of a spacer layer S is shorter than spin diffusion length in apinned layer P and a free layer F mentioned later. For example, spindiffusion length of nickel iron (NiFe) is about 5 nm. From theviewpoint, as for the thickness of the spacer layer S, thinner isbetter.

If resistance in case a conduction electron passes a spacer layer S ishigh, a problem that MR rate of change falls will arise. Also from thisviewpoint, the thinner is better as for the thickness of the spacerlayer S.

On the other hand, also when the magnetization direction of a free layerF changes with medium magnetic fields, magnetic coupling between apinned layer P and a free layer F must be divided so that change may notarise in the magnetization direction of a pinned layer P.

Thus, considering a viewpoint of dividing magnetic coupling between thepinned layer P and the free layer F, the spacer layer S needs to have acertain thickness.

In the case of a spacer layer S formed only with metal, about 1.5 nm ofthe thickness is the minimum of the thickness. Therefore, as thicknessof a spacer layer S, 1.5 nm-5 nm is desirable, and 2 nm-4 nm is stillmore desirable.

However, in order to constrict the current path in a spacer layer S inthe case of CCP-CPP (Current Confined Path Current Perpendicular toPlane) type structure which is mentioned in the next example, an oxideis included in a spacer layer S. In the case of such CCP-CPP typestructure, magnetic coupling between a pinned layer P and a free layer Ftends to be weak by existence of an oxide layer which produces the CCPeffect. Therefore, it becomes possible to make the thickness of thecopper (Cu) layers which exist in the upper and lower sides of the CCPspacer thinner than 1.5 nm. For example, it becomes possible to makethen thickness of the copper (Cu) spacer layers in the upper and lowersides of an oxide layer for CCP down to 0.1 nm.

As an oxide layer which produces the CCP effect, a tantalum (Ta) oxide,a chromium (Cr) oxide, a titanium (Ti) oxide, a zirconium (Zr) oxide, ahafnium (Hf) oxide, an aluminum (Al) oxide, a silicon (Si) oxide, amagnesium (Mg) oxide, a vanadium (V) oxide, a tungsten (W) oxide, amolybdenum (Mo) oxide, etc. can be mentioned. Thickness of the oxidelayer at this time is preferably about 1 nm-3 nm.

Table 6 shows examples of the spacer layer S.

The invention makes it a main purpose to pull out the CPP effect.However, in the case of the TMR (Tunneling Magnetoresistance) effect,the conduction half metal effect of the invention is also effective. Thenon-magnetic spacer layer in TMR, such Al₂O₃, MgO, SiO₂, HfO₂, andSrTiO₃, can be used as a very thin oxide layer TB of the invention. Inthis case, 1 nm-3 nm is desirable as the thickness of the oxide layer.Since there are restrictions that resistance must not be increased asalready stated in applying to a magnetic head, the desirable thicknessmay be 1 nm-2 nm.

The cobalt iron (CoFe) 1 nm/nickel iron (NiFe) 4 nm on the spacer layerS are free layers F. It is the layer at which the magnetizationdirection changes with medium magnetic fields. The cobalt iron (CoFe) 1nm/nickel iron (NiFe) 4 nm are the standard free layers currently usedfrom a generation of CIP (Current-In-Plane) type.

In this case, the cobalt iron (CoFe) layer of 1 nm-thick at theinterface with the spacer layer S is an interface layer for suppressinga mixing of the spacer layer S and the nickel iron (NiFe) layer. Thenickel iron (NiFe) layer is a soft magnetic layer.

However, it may differ from a CIP type and, in a CPP type case, a layerof 1 nm (CoFe) of cobalt iron between a spacer layer S and a free layerF may not necessarily be needed. The spin dependent interface scatteringeffect between the spacer layer S and the free layer F in the statewhere current concentrated on the spacer layer S is produced in a caseof CIP type element. On the other hand, the spin dependent interfacedependence scattering effect is produced when current passes throughbetween interfaces of the spacer layer S and the free layer Fcompulsorily in the case of CPP type element. A mixing layer of a nickeliron (NiFe) layer and a copper (Cu) layer may not reduce the spindependent interface dependence scattering effect. That is, the mixingeffect would not be the same for CIP type and for CPP type structure.

As composition of nickel iron (NiFe), nickel70Fe30-nickel90Fe10 ispreferred, and the range of nickel78Fe22-nickel83Fe17 is still morepreferred. As film structure which raises the spin dependent bulkscattering effect in inside of the free layer F, a nickel iron cobalt(NiFeCo) film, cobalt iron (CoFe)/nickel iron cobalt (NiFeCo) laminatedconstitution, (NiFeCo/CuO.1 nm)×n laminated structure, etc. can bementioned.

As the composition of the nickel iron cobalt (NiFeCo) layer, thecomposition around nickel66Fe16Co18 is preferable, because at thatcomposition, fcc structure appears and magnetic distortion tends tobecome zero. As for thickness of copper (Cu) when laminating copper (Cu)on nickel iron cobalt (NiFeCo), it is preferred to set it down to a verythin level, to about 0.1nm-1 nm. By inserting such a very thin copper(Cu) layer, the spin dependent bulk scattering effect in the inside ofthe free layer F increases, and MR rate of change increases. Sincemagnetic coupling of a magnetic layer of the upper and lower sidesthrough the copper layer will go out if copper (Cu) thickness becomesthicker than 1 nm too much, and it stops functioning as the united freelayer F, it is not desirable.

Since a cycle of inserting copper (Cu) layers to the free layer F alsobrings a difference to MR rate of change, it is important. As athickness interval to insert the copper (Cu) layers repeatedly, 0.5 nm-3nm is preferred, and 0.7 nm-2 nm is more preferred.

Not only a case of nickel iron cobalt (NiFeCo) but also in the case ofnickel iron (NiFe), insertion of such a very thin copper (Cu) layerbrings about MR rate of change. Therefore, (NiFe/Cu)×n laminatedstructure may be adopted. A single layer of CoFe can also be used as afree layer. A laminated structure of (CoFe/Cu)×n can also be used. Asthe inserting layer for such a laminated structure, a layer made ofcopper (Cu), zirconium (Zr), hafnium (Hf), niobium (Nb), or materiallike gallium (Ga) is usable. The thickness of these inserting layers maypreferably in a range 0.1 nm-1 nm. By inserting such a layer into thefree layer, spin-dependent bulk scattering effect in the free layer maybe enhanced, and thus, MR may be improved.

In this example, a magnetic layer is not mixed as an addition element,but very thin layers are inserted at intervals of a certain fixedthickness. In such a case, it is desirable to insert element materialwhich does not form a solid solution with the element which constitutesthe magnetic layer. For example, when a zirconium (Zr), a hafnium (Hf),etc. are used, MR rate of change improves and it is especiallydesirable.

Such existence of a very thin metal layer can be observed by a sectionTEM (Transmission Electron Microscopy) from a film section etc. evenafter the heat treatment for magnetization pinning of anantiferromagnetic layer in a magnetic field. When it contained as anaddition element simply in a magnetic layer, big concentrationdistribution is not seen in the direction of a film section. On theother hand, when it inserts as an independent layer like this example,it can observe by a section TEM. By using a nano-EDX (energy dispersivex-ray spectroscopy) of about 1 nm of diameters of beam spot (it is moredesirable as smaller than this diameter of spot) is observable asconcentration distribution of a structure element by measuring atintervals of 1 nm or less in the direction of thickness.

However, as mentioned above, the inserted thickness may be about 0.1 nm.When EDX analysis of such a very thin layer is carried out with about 1nm of diameters of beam spot, as a result of EDX analysis, it will bedetected as concentration of number atom % also in an area in which avery thin layer exists. However, it is possible by scanning the samemeasurement in the direction of thickness to identify in an area where avery thin layer element layer exists, and an area which is not carriedout.

Table 7 shows the examples of other free layer F.

In this example, a copper (Cu) layer laminated on a free layer Ffunctions also as a prevention layer of interface mixing with tantalumon it (Ta). Instead of copper (Cu), gold (Au), silver (Ag), a ruthenium(Ru), rhodium (Rh), palladium (Pd), etc. may be used.

This layer can also be lost, when interface mixing with a cap layer isprevented. As for the thickness of this layer, it is preferred that itis 0 nm-about 3 nm.

A copper (Cu) layer on a free layer F and a tantalum (Ta) layerlaminated on it are called a “cap layer” here. This is for protecting sothat a lamination film may not be etched, also when the microfabrication process after spin valve film formation is performed.Instead of a tantalum (Ta) layer, titanium (Ti), zirconium (Zr),ruthenium (Ru), niobium (Nb), tungsten (W), hafnium (Hf), rhenium (Re),iridium (Ir), gold (Au), silver (Ag), etc. can be used as a protectionlayer.

Table 8 shows the examples of the cap layer.

On the other hand, since controlling the crystal orientation of a spinvalve film also affects MR rate of change as mentioned above, it isimportant. By controlling crystal orientation, crystal defects within aspin dependence scattering unit of pinned layer P/spacer layer S/freelayer F may be decreased. As the result, spin information on an up spinand a down spin is not lost, and spin diffusion length in a laminatedstructure can be lengthened enough. That is, even if total thickness ofpinned layer P/spacer layer S/free layer F becomes thick, the spindependence bulk scattering effect can fully be obtained, and MR rate ofchange improves.

The coherency of the laminated structure also improves by controllingcrystal orientation. Therefore, the spin dependent interface scatteringeffect improves and MR rate of change improves.

Good crystal band structure is formed by controlling crystalorientation. Therefore, a band structural change by insertion of verythin metal layers, such as a copper (Cu) layer of a very thin and azirconium (Zr) layer of a very thin, which was mentioned above becomeseasy to appear notably. As the result, improvement in MR rate of changeresulting from band structure becomes more remarkable. For example, whenband structure changes, a difference of the Fermi speed of an up spinand a down spin becomes large. This phenomenon becomes more remarkablein a spin valve film with good crystal orientation.

The invention is an aiming at band structure modulation of a crystal.Therefore, when crystal orientation changes, naturally an effect of avery thin oxide layer will change. When a pinned layer P or a free layerF has fcc structure, it is desirable to have fcc (111) orientation. Whena pinned layer P or a free layer F has bcc structure, it is desirable tohave bcc (110) orientation. When the pinned layer P or the free layer Fhas hcp structure, it is desirable to have for hcp (001) orientation orhcp (110) orientation.

As for the orientation variation angle, it is preferred that it is lessthan 5.0 degrees, and it is still preferred that it is less than 3.5degrees and it is still more preferred that it is less than 3.0 degrees,and that it is most preferred that it is less than 4.0 more degrees.

A film having an excellent crystal orientation can obtain high MR rateof change. That is, high output voltage can be obtained.

This reason is explained below. The very thin oxide layer in theinvention aims at modulating the band structure of a magnetic layer.Band structure can be defined about what naturally has a crystalstructure. That is, more perfect crystal structure is acquired, theeffect of the band modulation of a the invention shows up more notably,and the rise effect of MR rate of change becomes larger.

The quality of a crystal corresponds to a distribution angle of thecrystal orientation. Therefore, the band modulation effect by theinvention becomes large and MR rate becomes large, as the distributionangle becomes small.

Concretely, when the distribution angle 6 degrees, the increasing rateof MR rate of change by having inserted the very thin oxide layer by theinvention was as small as about 1.1 times. On the other hand, when thedistribution angle was 5 degrees, the increasing rate of MR was twice.Moreover, when the distribution angle was 4 degrees, the increasing rateof MR was three times. When the distribution angle was 3.5 degrees, theincreasing rate of MR was 4 times. When the distribution angle was 3degrees, the increasing rate of MR was 5 times. These data were obtainedwith samples where only one very thin oxide layer was inserted.Therefore, by inserting two or more very thin oxide layers, furtherimprovement can be attained.

In measurement by X-rays, crystal orientation can be measured as halfwidth of a rocking curve in a peak position obtained by θ-2θmeasurement. In a magnetic head, it is detectable as a distributionangle of a spot in a nano-diffraction pattern taken from sectionstructure. As for the crystal orientation of the polycrystalline films,the definition of the terms and its measurement procedures, thosedescribed in U.S. Pat. No. 6,395,388 can be referred to. The entirecontents of this reference is incorporated herein by reference. Althoughit is dependent also on material of an antiferromagnetic film, generallythe lattice spacing of the antiferromagnetic film differs from latticespacing of pinned layer P/spacer layer S/free layer F. Therefore, it ispossible to calculate separately a variation angle for orientation ineach layer.

For example, platinum manganese (PtMn), and pinned layer P/spacer layerS/free layer F become the structure that lattice spacing differ, in manycases. Since platinum manganese (PtMn) is formed comparatively thickly,it is the material suitable for measuring the crystal orientationvariation. As for pinned layer P/spacer layer S/free layer F, crystalstructures of a pinned layer P and a free layer F may differ like bccstructure and fcc structure. Therefore, the pinned layer P and the freelayer F have a distribution angle s for respectively different crystalorientations.

Next, an example about a formation method of a very thin oxide layer TBin the embodiment will be explained.

FIG. 24 is a conceptual diagram showing an example of a formationapparatus which forms a magnetoresistance effect element containing avery thin oxide layer TB in the embodiment. That is, in the case of aapparatus of this figure, it has structure where a load lock chamber LCwhich introduces a substrate, film formation chambers MC1, MC2, and TBC,a surface treatment chamber PC, etc. are connected via a vacuum valve V,via a transfer chamber TC.

In metal film formation chambers MC1 and MC2, film formation of a metalfilm used as a basic unit of a spin valve film is formed with methodsfor film deposition, such as a sputtering. Specifically, sputtering filmformation of various kinds of methods of DC magnetron film formation, RFmagnetron sputtering, and others and IBD (Ion Beam Deposition) may beused. Vapor deposition film formation, MBE (Molecular Beam Epitaxy),etc. may also be used. A very thin oxide layer TB in the embodiment,such as an oxide layer and a nitride layer, may be formed by these filmformation chambers.

It is also the desirable manufacture method of a very thin oxide layer,to perform formation of an oxide layer used as a very thin oxide layerTB of the embodiment or a nitride layer in a surface treatment chamberPC on the other hand. Specifically, natural oxidation, the naturalnitriding method, UV (ultraviolet rays) light irradiation in the radicaloxidizing (nitride) method and oxygen atmosphere, the ozone oxidizingmethod, the ion beam oxidizing method, etc. can be used.

The oxidization technique with the energy assistant effect is moredesirable than a natural oxidation method. For example, since the ionbeam oxidizing method etc. has the energy assistant effect by an ionbeam, it is effective. Then, oxygen gas may be irradiated as an ion beamand an ion beam of rare gas, such as argon (Ar), xenon (Xe), and krypton(Kr), may be irradiated in oxygen atmosphere.

Since thickness of an oxide layer or a nitride layer will become thickif energy of a beam is too high at this time, the degree of beamincidence angle also has low angle incidence more preferred thanperpendicular incidence with energy of a grade which is not too high.

For example, in the case of 90-degree incidence, 50V-150V have thedesirable degree of incidence angle as accelerating voltage of an ionbeam to the main side of a substrate, and when the degree of incidenceangle is the low angle incidence which is 10-30 degrees, about 50-300Vis desirable as accelerating voltage of an ion beam.

However, in oxidization and a nitride using the conventional ion beam,energy spreads in the direction as the degree of beam incidence anglewhere energy of a beam is the same.

Therefore, even if the accelerating voltage of a beam is lowered or thedegree of incidence angle is made into low angle incidence, it arisesthat thickness of an oxide film becomes thick depending on material ofthe surface which oxidizes. As a method of controlling this further, amethod of using GC-IB (Gas Cluster Ion-Beam) which is the ion beam of acluster state instead of an ion beam of the conventional monomer can bementioned.

In the case of this method, when it is accelerated in the state of acluster and an ion beam collides with the sample surface, a clusterbursts with quantity of motion in the direction of the film surface.Thus, a high-concentration gas molecule has the energy to the directionof a film plane (getting it blocked and there being no damage to thedirection of thickness), and collides. If an oxygen cluster is used as agas molecule, it is compatible in oxide formation by high energyoxidization and formation in a very thin level. By adjusting the numberof gas clusters, oxygen concentration per unit surface area can beadjusted. Therefore, the valence number can be also controlled.

SECOND EXAMPLE

Next, the example of the CPP type magnetoresistance effect element whichcan be used as a magnetic head is given and explained as the secondexample of the invention.

FIGS. 25 and 26 are conceptual diagrams which express typically theprincipal part structure of the magnetoresistance effect elementconcerning the embodiment of the invention. That is, these figuresexpress the state where the magnetoresistance effect element is includedin the magnetic head. FIG. 25 is a sectional view of themagnetoresistance effect element cut in parallel to the medium facingsurface P which is opposite to a magnetic recording medium (not shown).FIG. 26 is a sectional view of the magnetic resistance effect elementcut in the perpendicular direction to the medium opposite side P.

The magnetoresistance effect element illustrated in FIGS. 25 and 26 hasa hard abutted structure. The lower electrode 2 and the upper electrode6 are provided in the upper and lower sides of the magnetoresistanceeffect film 4, respectively. Moreover, as expressed in FIG. 25, the biasmagnetic field applying film 10 and the insulating film 12 are laminatedand provided in the both sides of the magnetoresistance effect film 4.Furthermore, as illustrated in FIG. 26, the protection layer 8 isprovided in the medium facing surface of the magnetoresistance effectfilm 4.

The magnetoresistance effect film 4 has the structure according to theembodiment of the invention mentioned above referring to FIGS. 1 and 24.That is, the very thin oxide layer is suitably inserted in themagnetoresistance effect film, and a large resistance change can beobtained by CPP type current supply.

The sense current to the magnetoresistance effect film 4 is passed in aperpendicular direction to the film plane, as indicated by the arrow A,with the electrodes 2 and 6 arranged at the upper and lower sides.Moreover, a bias magnetic field is applied to the magnetoresistanceeffect film 4 with a pair of bias magnetic field applying films 10 and10 provided in right and left.

By this bias magnetic field, magnetic anisotropy of the free layer ofthe magnetoresistance effect film 4 can be controlled and formed into asingle magnetic domain. As a result, magnetic domain structure can bestabilized, and the Barkhausen noise due to the movement of magneticwall can be suppressed.

According to the invention, MR rate of change improves by providing thevery thin oxide layer suitably in the magnetoresistance effect film 4.As a result, it becomes possible to improve the sensitivity of amagnetoresistance effect element notably. And for example, when it isapplied to a magnetic head, magnetic reproduction of high sensitivity isattained.

THIRD EXAMPLE

Next, a magnetic reproducing apparatus having inboard themagnetoresistance effect element of the embodiment will be explained asthe third example of the invention.

That is, the magnetoresistance effect element or the magnetic headexplained with reference to FIGS. 1 through 26 can be incorporated in arecording/reproducing magnetic head assembly and mounted in a magneticreproducing apparatus.

FIG. 27 is a perspective view that shows outline configuration of thiskind of magnetic reproducing apparatus. The magnetic reproducingapparatus 150 shown here is of a type using a rotary actuator. Amagnetic reproducing medium disk 200 is mounted on a spindle 152 androtated in the arrow A direction by a motor, not shown, which isresponsive to a control signal from a controller of a driving mechanism,not shown. The magnetic reproducing apparatus 150 shown here may have aplurality of medium disks 200 inboard.

The medium disk 200 may be of a “lateral recording type” in whichdirections of the recording bits are substantially in parallel to thedisk surface or may be of a “perpendicular recording type” in whichdirections of the recording bits are substantially perpendicular to thedisk surface.

A head slider 153 for carrying out recording and reproduction ofinformation to be stored in the medium disk 200 is attached to the tipof a film-shaped suspension 154. The head slider 153 supports amagnetoresistance effect element or magnetic head, for example,according to one of the foregoing embodiments of the invention, near thedistal end thereof.

Once the medium disk 200 rotates, the medium-facing surface (ABS) of thehead slider 153 is held floating by a predetermined distance above thesurface of the medium disk 200. Also acceptable is a so-called“contact-traveling type” in which the slider contacts the medium disk200.

The suspension 154 is connected to one end of an actuator arm 155 havinga bobbin portion for holding a drive coil, not shown, and others. At theopposite end of the actuator arm 155, a voice coil motor 156, a kind oflinear motor, is provided. The voice coil motor 156 comprises a drivecoil, not shown, wound on the bobbin portion of the actuator arm 155,and a magnetic circuit made up of a permanent magnet and an opposed yokethat are opposed to sandwich the drive coil.

The actuator arm 155 is supported by ball bearings, not shown, which arelocated at upper and lower two positions of the spindle 157 and drivenby the voice coil motor 156 for rotating, sliding movements.

FIG. 28 is a perspective view of a magnetic head assembly at the distalend from an actuator arm 155 involved, which is viewed from the disk.The magnetic head assembly 160 includes the actuator arm 155 having thebobbin portion supporting the drive coil, for example, and thesuspension 154 is connected to one end of the actuator arm 155.

At the distal end of the suspension 154, a head slider 153 carrying themagnetoresistance effect element as explained with reference to FIGS. 1through 24 is provided. The suspension 154 has a lead 164 for writingand reading signals, and the lead line 164 is connected to electrodes ofthe magnetic head incorporated in the head slider 153. Numeral 165 inFIG. 28 denotes an electrode pad of the magnetic head assembly 160.

According to this example, one of the magnetoresistance effect elementsalready explained in conjunction with the aforementioned embodiments isused as the magnetoresistance effect element, information magneticallyrecorded on the medium disk 200 under a higher recording density thanbefore can be read reliably.

FOURTH EXAMPLE

Next, a magnetic memory having the magnetoresistance effect element ofthe embodiment will be explained as the fourth example of the invention.That is, a magnetic memory, such as a magnetic random access memory(MRAM), where memory cells are arranged in the shape of a matrix can berealized by using the magnetoresistance effect element of theembodiment.

FIG. 29 is a conceptual diagram which exemplifies the matrix structureof the magnetic memory of the embodiment. That is, this figure shows thecircuit structure of the embodiment in the case of having arranged thememory cells each of which includes a magnetoresistance effect elementmentioned above with reference to FIGS. 1 through 24, in the shape of amatrix array.

In order to choose one bit in an array, it has the sequence decoder 350and the line decoder 351. By selecting the bit line 334 and the wordline 332, specific switching transistor 330 is turned on and a specificcell is chosen uniquely. And the bit information recorded on themagnetic-recording layer which constitutes the magnetoresistance effectelement 321 can be read by detecting with a sense amplifier 352.

When writing in bit information, writing current is passed in thespecific write-in word line 323 and the specific bit line 322,respectively, and the current magnetic field is applied to the recordinglayer of a specific cell.

FIG. 30 is a conceptual diagram showing another example of the matrixstructure of the magnetic memory of the embodiment. That is, in the caseof this example, the bit lines 322 and word lines 334 which were wiredin the shape of a matrix are chosen by decoders 360 and 361,respectively, and the specific memory cell in an array is chosenuniquely.

Each memory cell has the structure where Diode D is connected with themagnetoresistance effect element 321 in series.

Here, Diode D has the role to prevent that sense current detours inmemory cells other than magnetoresistance effect element 321 selected.

In writing, write-in current is passed in a specific bit line 322 and aword line 323, thereby applying the current magnetic field to therecording layer of a specific cell.

FIG. 31 is a conceptual diagram showing a principal part of the crosssectional structure of a magnetic memory according to an embodiment ofthe invention.

And FIG. 32 shows the A-A′ line sectional view.

That is, the structure shown in these figures corresponds to the memorycell of the 1-bit portion of the magnetic memory which operates as arandom access memory.

This memory cell consists of a storage cell portion 311 and a transistorportion 312 for address selection. The storage cell portion 311 has themagnetoresistance effect element 321 and a pair of wiring 322 and 324connected to the element 321. The magnetoresistance effect element 321has a structure mentioned with reference to FIGS. 1 through 24, andshows a large magnetoresistance effect.

What is necessary is to pass sense current for the magnetoresistanceeffect element 321 in the case of bit information read-out, and just todetect the resistance change. In addition, the magnetization free layerof the magnetoresistance effect element can be used as the magneticrecording layer.

If the element 4 has a ferromagnetic double tunnel junction structuresuch as magnetic layer/non-magnetic tunnel layer/magneticlayer/non-magnetic tunnel layer/magnetic layer etc., it is advantageousat a point that the high magnetoresistance effect is acquired by a largeresistance change by the tunnel magnetoresistance (TMR) effect.

In such structures, one of magnetic layers shall act as a magnetizationpinned layer, and one of other magnetic layers shall act as a magneticrecord layer.

A selecting transistor 330 connected through a via 326 and buried wiring328 is formed in a transistor portion 312 for selection. This transistor330 carries out switching operation according to the voltage applied toa gate 332, and controls switching of the current path between themagnetoresistance effect element 321 and wiring 334.

Moreover, under the magnetoresistance effect element, the write-inwiring 323 is formed in the direction which intersects the wiring 322.These write-in wirings 322 and 323 can be formed with the alloycontaining aluminum (aluminum), copper (Cu), tungsten (W), tantalum(Ta), or one of these.

In a memory cell of such structure, when writing bit information in themagnetoresistance effect element 321, a write-in pulse current is passedto the wirings 322 and 323. Then, a synthetic magnetic field induced bythese current is applied to a record layer, and magnetization of arecord layer of the magnetoresistance effect element can be reversedsuitably.

On the other hand, when reading bit information, sense current is passedthrough wiring 322, the magnetoresistance element 321 containing amagnetic-recording layer, and the lower electrode 324, and a change ofthe resistance of the magnetoresistance effect element 321 or resistanceitself is measured.

By using the magnetoresistance effect element mentioned with referenceto FIGS. 1 through 24, a large magnetoresistance effect is obtained.Therefore, a stable read-out can be performed even if the cell size isreduced to realize a large capacity storage.

Heretofore, embodiments of the invention have been explained in detailwith reference to some specific examples. The invention, however, is notlimited to these specific examples.

For example, material, shape and thickness of the ferromagnetic layer,anti-ferromagnetic layer, insulating film and very thin oxide layer ofthe magnetoresistance effect element according to the invention may beappropriately selected by those skilled in the art within the knowntechniques to carry out the invention as taught in the specification andobtain equivalent effects.

Further, in a case where the magnetoresistance effect element of theinvention is applied to a magnetic head, by providing magnetic shieldson upper and lower side of the element, the reproducing resolution canbe regulated.

It will be also appreciated that the invention is applicable not only tooptically-assisted magnetic heads or magnetic recording apparatuses ofthe lengthwise recording type but also to those of the perpendicularmagnetic recording type and ensures substantially the same effects.

Further, the magnetic reproducing apparatus according to the presentinvention may be of a fixed type in which specific magnetic recordingmedium is permanently installed, while it may be of a removable type inwhich the magnetic recording medium can be replaced easily.

Further, also concerning the magnetic memory according to the invention,those skilled in the art will be able to carry out the invention byappropriately selecting a material or a structure within the knowntechniques.

While the present invention has been disclosed in terms of theembodiment in order to facilitate better understanding thereof, itshould be appreciated that the invention can be embodied in various wayswithout departing from the principle of the invention. Therefore, theinvention should be understood to include all possible embodiments andmodification to the shown embodiments which can be embodied withoutdeparting from the principle of the invention as set forth in theappended claims.

1. A magnetoresistance effect element comprising: a magnetoresistance effect film having: a first magnetic layer whose direction of magnetization is substantially pinned in one direction; a second magnetic layer whose direction of magnetization changes in response to an external magnetic field; a nonmagnetic intermediate layer located between the first and second magnetic layers; and a film provided in the first magnetic layer, in the second magnetic layer, at an interface between the first magnetic layer and the nonmagnetic intermediate layer, or at an interface between the second magnetic layer and the nonmagnetic intermediate layer, the film having a thickness not larger than 3 nanometers, and the film having at least one selected from the group consisting of nitride, oxynitride, phosphide, and fluoride; and a pair of electrodes electrically coupled to the magnetoresistance effect film and configured to supply a sense current perpendicularly to a film plane of said magnetoresistance effect film.
 2. The magnetoresistance effect element according to claim 1, comprising two of the films and the films being formed either two of the positions in the second magnetic layer, at an interface between the first magnetic layer and the nonmagnetic intermediate layer, and an interface between the second magnetic layer and the nonmagnetic intermediate layer.
 3. The magnetoresistance effect element according to claim 2, wherein a distance between the neighboring films is in a range between 0.2 nanometers and 3 nanometers.
 4. The magnetoresistance effect element according to claim 1, wherein the first or second magnetic layer which includes or adjoins the film is made of a ferromagnetic material including at least one selected from the group consisting of iron (Fe), cobalt (Co), and nickel (Ni).
 5. The magnetoresistance effect element according to claim 1, wherein the film includes at least one element selected from the group consisting of magnesium (Mg), aluminum (Al), silicon (Si), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), copper (Cu), zinc (Zn), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), hafnium (Hf), tantalum (Ta), tungsten (W), technetium (Tc), rhenium (Re), Osmium (Os), iridium (Ir), platinum (Pt) and gold (Au).
 6. The magnetoresistance effect element according to claim 1, further comprising a nonmagnetic metal layer adjoining the film and provided in the first and/or second magnetic layer, the nonmagnetic metal layer having a thickness equal to or smaller than 2 nanometers.
 7. The magnetoresistance effect element according to claim 1, further comprising a nonmagnetic metal layer adjoining the film and provided at an interface between the first magnetic layer and the nonmagnetic intermediate layer, and/or at an interface between the second magnetic layer and the nonmagnetic intermediate layer, the nonmagnetic metal layer having a thickness equal to or smaller than 2 nanometers.
 8. The magnetoresistance effect element according to claim 1, further comprising: a magnetic metal layer adjoining the film and provided in the first and/or second magnetic layer; and a nonmagnetic layer adjoining the magnetic metal layer, and having a thickness equal to or smaller than 2 nanometers.
 9. The magnetoresistance effect element according to claim 1, further comprising a magnetic metal layer adjoining the film and provided at an interface between the first magnetic layer and the nonmagnetic intermediate layer, and/or at an interface between the second magnetic layer and the nonmagnetic intermediate layer; and a nonmagnetic layer adjoining the magnetic metal layer, and having a thickness equal to or smaller than 2 nanometers.
 10. The magnetoresistance effect element according to claim 8, wherein the first or second magnetic layer is magnetically coupled through the film, the magnetic metal layer and the nonmagnetic metal layer included within its layer.
 11. The magnetoresistance effect element according to claim 1, wherein a distance between the film and the nonmagnetic intermediate layer is equal to or smaller than three nanometers.
 12. A magnetoresistance effect element comprising: a magnetoresistance effect film having: a first magnetic layer whose direction of magnetization is substantially pinned in one direction; a second magnetic layer whose direction of magnetization changes in response to an external magnetic field; a nonmagnetic intermediate layer located between the first and second magnetic layers; and a plurality of films are provided in at least two of the first magnetic layer, the second magnetic layer, at an interface between the first magnetic layer and the nonmagnetic intermediate layer, and at an interface between the second magnetic layer and the nonmagnetic intermediate layer, and the film having at least one selected from the group consisting of nitride, oxynitride, phosphide, and fluoride; and a pair of electrodes electrically coupled to the magnetoresistance effect film to supply a sense current perpendicularly to a film plane of said magnetoresistance effect film, wherein a product AR of an area A and resistance R is equal to or smaller than 500 mΩμm², where the area A is an area of a portion of the magnetoresistance effect film that the sense current substantially passes through, and the resistance R is a resistance obtained between the pair of electrodes, or a resistance R between the pair of electrodes is equal to or smaller than 100Ω.
 13. The magnetoresistance effect element according to claim 12, wherein a distance between the neighboring films is in a range between 0.2 nanometers and 3 nanometers.
 14. The magnetoresistance effect element according to claim 12, further comprising a nonmagnetic metal layer adjoining the film and provided in the first and/or second magnetic layer, the nonmagnetic metal layer having a thickness equal to or smaller than 2 nanometers.
 15. The magnetoresistance effect element according to claim 12, further comprising a nonmagnetic metal layer adjoining the film and provided at an interface between the first magnetic layer and the nonmagnetic intermediate layer, and/or at an interface between the second magnetic layer and the nonmagnetic intermediate layer, the nonmagnetic metal layer having a thickness equal to or smaller than 2 nanometers.
 16. The magnetoresistance effect element according to claim 12, further comprising: a magnetic metal layer adjoining the film and provided in the first and/or second magnetic layer; and a nonmagnetic layer adjoining the magnetic metal layer, and having a thickness equal to or smaller than 2 nanometers.
 17. The magnetoresistance effect element according to claim 12, further comprising a magnetic metal layer adjoining the film and provided at an interface between the first magnetic layer and the nonmagnetic intermediate layer, and/or at an interface between the second magnetic layer and the nonmagnetic intermediate layer; and a nonmagnetic layer adjoining the magnetic metal layer, and having a thickness equal to or smaller than 2 nanometers.
 18. The magnetoresistance effect element according to claim 16, wherein the first or second magnetic layers are magnetically coupled through the film, the magnetic metal layer and the nonmagnetic metal layer.
 19. A magnetic head comprising a magnetoresistance effect element having; a magnetoresistance effect film having: a first magnetic layer whose direction of magnetization is substantially pinned in one direction; a second magnetic layer whose direction of magnetization changes in response to an external magnetic field; a nonmagnetic intermediate layer located between the first and second magnetic layers; and a film provided in the first magnetic layer, in the second magnetic layer, at an interface between the first magnetic layer and the nonmagnetic intermediate layer, or at an interface between the second magnetic layer and the nonmagnetic intermediate layer, the film having a thickness not larger than 3 nanometers, and the film having at least one selected from the group consisting of nitride, oxynitride, phosphide, and fluoride; and a pair of electrodes electrically coupled to the magnetoresistance effect film and configured to supply a sense current perpendicularly to a film plane of said magnetoresistance effect film.
 20. A magnetic reproducing apparatus which reads information magnetically recorded in a magnetic recording medium, the magnetic reproducing apparatus comprising a magnetic head having a magnetoresistance effect element including: a magnetoresistance effect film having: a first magnetic layer whose direction of magnetization is substantially pinned in one direction; a second magnetic layer whose direction of magnetization changes in response to an external magnetic field; a nonmagnetic intermediate layer located between the first and second magnetic layers; and a film provided in the first magnetic layer, in the second magnetic layer, at an interface between the first magnetic layer and the nonmagnetic intermediate layer, or at an interface between the second magnetic layer and the nonmagnetic intermediate layer, the film having a thickness not larger than 3 nanometers, and the film having at least one selected from the group consisting of nitride, oxynitride, phosphide, and fluoride; and a pair of electrodes electrically coupled to the magnetoresistance effect film and configured to supply a sense current perpendicularly to a film plane of said magnetoresistance effect film.
 21. A magnetic memory comprising a plurality of magnetoresistance effect elements arranged in a matrix fashion, the magnetoresistance effect element including: a magnetoresistance effect film having: a first magnetic layer whose direction of magnetization is substantially pinned in one direction; a second magnetic layer whose direction of magnetization changes in response to an external magnetic field; a nonmagnetic intermediate layer located between the first and second magnetic layers; and a film provided in the first magnetic layer, in the second magnetic layer, at an interface between the first magnetic layer and the nonmagnetic intermediate layer, or at an interface between the second magnetic layer and the nonmagnetic intermediate layer, the film having a thickness not larger than 3 nanometers, and the film having at least one selected from the group consisting of nitride, oxynitride, phosphide, and fluoride; and a pair of electrodes electrically coupled to the magnetoresistance effect film and configure to supply a sense current perpendicularly to a film plane of said magnetoresistance effect film. 